diff --git a/src/access/isSuperAdmin.ts b/src/access/isSuperAdmin.ts
new file mode 100644
index 0000000..f449243
--- /dev/null
+++ b/src/access/isSuperAdmin.ts
@@ -0,0 +1,10 @@
+import type { Access } from 'payload'
+import { User } from '../payload-types'
+
+export const isSuperAdminAccess: Access = ({ req }): boolean => {
+  return isSuperAdmin(req.user)
+}
+
+export const isSuperAdmin = (user: User | null): boolean => {
+  return Boolean(user?.roles?.includes('super-admin'))
+}
diff --git a/src/collections/Tenants/access/byTenant.ts b/src/collections/Tenants/access/byTenant.ts
new file mode 100644
index 0000000..05fc99a
--- /dev/null
+++ b/src/collections/Tenants/access/byTenant.ts
@@ -0,0 +1,39 @@
+import type { Access } from 'payload'
+
+import { isSuperAdmin } from '../../../access/isSuperAdmin'
+
+export const filterByTenantRead: Access = (args) => {
+  // Allow public tenants to be read by anyone
+  if (!args.req.user) {
+    return {
+      allowPublicRead: {
+        equals: true,
+      },
+    }
+  }
+
+  return true
+}
+
+export const canMutateTenant: Access = ({ req }) => {
+  if (!req.user) {
+    return false
+  }
+
+  if (isSuperAdmin(req.user)) {
+    return true
+  }
+
+  return {
+    id: {
+      in:
+        req.user?.tenants
+          ?.map(({ roles, tenant }) =>
+            roles?.includes('tenant-admin')
+              ? tenant && (typeof tenant === 'string' ? tenant : tenant.id)
+              : null,
+          )
+          .filter(Boolean) || [],
+    },
+  }
+}
diff --git a/src/collections/Tenants/access/updateAndDelete.ts b/src/collections/Tenants/access/updateAndDelete.ts
new file mode 100644
index 0000000..2a51e96
--- /dev/null
+++ b/src/collections/Tenants/access/updateAndDelete.ts
@@ -0,0 +1,19 @@
+import { isSuperAdmin } from '@/access/isSuperAdmin'
+import { getUserTenantIDs } from '@/utilities/getUserTenantIds'
+import { Access } from 'payload'
+
+export const updateAndDeleteAccess: Access = ({ req }) => {
+  if (!req.user) {
+    return false
+  }
+
+  if (isSuperAdmin(req.user)) {
+    return true
+  }
+
+  return {
+    id: {
+      in: getUserTenantIDs(req.user, 'tenant-admin'),
+    },
+  }
+}
diff --git a/src/collections/Tenants/index.ts b/src/collections/Tenants/index.ts
index af6a368..f1b614e 100644
--- a/src/collections/Tenants/index.ts
+++ b/src/collections/Tenants/index.ts
@@ -1,15 +1,15 @@
 import type { CollectionConfig } from 'payload'
 
-//import { updateAndDeleteAccess } from './access/updateAndDelete'
-import { isSuperAdmin } from '@/access/admin'
+import { isSuperAdminAccess } from '@/access/isSuperAdmin'
+import { updateAndDeleteAccess } from './access/updateAndDelete'
 
 export const Tenants: CollectionConfig = {
   slug: 'tenants',
   access: {
-    create: isSuperAdmin,
-    delete: isSuperAdmin, // change these to the example soon!
-    read: ({ req }) => true,
-    update: isSuperAdmin,
+    create: isSuperAdminAccess,
+    delete: updateAndDeleteAccess,
+    read: ({ req }) => Boolean(req.user),
+    update: updateAndDeleteAccess,
   },
   admin: {
     useAsTitle: 'name',
diff --git a/src/collections/Users/access/create.ts b/src/collections/Users/access/create.ts
new file mode 100644
index 0000000..ecdf214
--- /dev/null
+++ b/src/collections/Users/access/create.ts
@@ -0,0 +1,24 @@
+import type { Access } from 'payload'
+
+import type { User } from '../../../payload-types'
+
+import { isSuperAdmin } from '../../../access/isSuperAdmin'
+import { getUserTenantIDs } from '@/utilities/getUserTenantIds'
+
+export const createAccess: Access<User> = ({ req }) => {
+  if (!req.user) {
+    return false
+  }
+
+  if (isSuperAdmin(req.user)) {
+    return true
+  }
+
+  const adminTenantAccessIDs = getUserTenantIDs(req.user, 'tenant-admin')
+
+  if (adminTenantAccessIDs.length) {
+    return true
+  }
+
+  return false
+}
diff --git a/src/collections/Users/access/isAccessingSelf.ts b/src/collections/Users/access/isAccessingSelf.ts
new file mode 100644
index 0000000..980a8b1
--- /dev/null
+++ b/src/collections/Users/access/isAccessingSelf.ts
@@ -0,0 +1,5 @@
+import { User } from '@/payload-types'
+
+export const isAccessingSelf = ({ id, user }: { user?: User; id?: string | number }): boolean => {
+  return user ? Boolean(user.id === id) : false
+}
diff --git a/src/collections/Users/access/read.ts b/src/collections/Users/access/read.ts
new file mode 100644
index 0000000..14ca302
--- /dev/null
+++ b/src/collections/Users/access/read.ts
@@ -0,0 +1,56 @@
+import type { User } from '@/payload-types'
+import type { Access, Where } from 'payload'
+import { getTenantFromCookie } from '@payloadcms/plugin-multi-tenant/utilities'
+
+import { isSuperAdmin } from '../../../access/isSuperAdmin'
+import { isAccessingSelf } from './isAccessingSelf'
+import { getCollectionIDType } from '@/utilities/getCollectionIDType'
+import { getUserTenantIDs } from '@/utilities/getUserTenantIds'
+
+export const readAccess: Access<User> = ({ req, id }) => {
+  if (!req?.user) {
+    return false
+  }
+
+  if (isAccessingSelf({ id, user: req.user })) {
+    return true
+  }
+
+  const superAdmin = isSuperAdmin(req.user)
+  const selectedTenant = getTenantFromCookie(
+    req.headers,
+    getCollectionIDType({ payload: req.payload, collectionSlug: 'tenants' }),
+  )
+  const adminTenantAccessIDs = getUserTenantIDs(req.user, 'tenant-admin')
+
+  if (selectedTenant) {
+    // If it's a super admin, or they have access to the tenant ID set in cookie
+    const hasTenantAccess = adminTenantAccessIDs.some((id) => id === selectedTenant)
+    if (superAdmin || hasTenantAccess) {
+      return {
+        'tenants.tenant': {
+          equals: selectedTenant,
+        },
+      }
+    }
+  }
+
+  if (superAdmin) {
+    return true
+  }
+
+  return {
+    or: [
+      {
+        id: {
+          equals: req.user.id,
+        },
+      },
+      {
+        'tenants.tenant': {
+          in: adminTenantAccessIDs,
+        },
+      },
+    ],
+  } as Where
+}
diff --git a/src/collections/Users/access/updateAndDelete.ts b/src/collections/Users/access/updateAndDelete.ts
new file mode 100644
index 0000000..018ec3f
--- /dev/null
+++ b/src/collections/Users/access/updateAndDelete.ts
@@ -0,0 +1,31 @@
+import type { Access } from 'payload'
+
+import { isSuperAdmin } from '@/access/isSuperAdmin'
+import { isAccessingSelf } from './isAccessingSelf'
+import { getUserTenantIDs } from '@/utilities/getUserTenantIds'
+
+export const updateAndDeleteAccess: Access = ({ req, id }) => {
+  const { user } = req
+
+  if (!user) {
+    return false
+  }
+
+  if (isSuperAdmin(user) || isAccessingSelf({ user, id })) {
+    return true
+  }
+
+  /**
+   * Constrains update and delete access to users that belong
+   * to the same tenant as the tenant-admin making the request
+   *
+   * You may want to take this a step further with a beforeChange
+   * hook to ensure that the a tenant-admin can only remove users
+   * from their own tenant in the tenants array.
+   */
+  return {
+    'tenants.tenant': {
+      in: getUserTenantIDs(user, 'tenant-admin'),
+    },
+  }
+}
diff --git a/src/collections/Users/endpoints/externalUsersLogin.ts b/src/collections/Users/endpoints/externalUsersLogin.ts
new file mode 100644
index 0000000..6b770f2
--- /dev/null
+++ b/src/collections/Users/endpoints/externalUsersLogin.ts
@@ -0,0 +1,130 @@
+import type { Collection, Endpoint } from 'payload'
+
+import { headersWithCors } from '@payloadcms/next/utilities'
+import { APIError, generatePayloadCookie } from 'payload'
+
+// A custom endpoint that can be reached by POST request
+// at: /api/users/external-users/login
+export const externalUsersLogin: Endpoint = {
+  handler: async (req) => {
+    let data: { [key: string]: string } = {}
+
+    try {
+      if (typeof req.json === 'function') {
+        data = await req.json()
+      }
+    } catch (error) {
+      // swallow error, data is already empty object
+    }
+    const { password, tenantSlug, tenantDomain, username } = data
+
+    if (!username || !password) {
+      throw new APIError('Username and Password are required for login.', 400, null, true)
+    }
+
+    const fullTenant = (
+      await req.payload.find({
+        collection: 'tenants',
+        where: tenantDomain
+          ? {
+            domain: {
+              equals: tenantDomain,
+            },
+          }
+          : {
+            slug: {
+              equals: tenantSlug,
+            },
+          },
+      })
+    ).docs[0]
+
+    const foundUser = await req.payload.find({
+      collection: 'users',
+      where: {
+        or: [
+          {
+            and: [
+              {
+                email: {
+                  equals: username,
+                },
+              },
+              {
+                'tenants.tenant': {
+                  equals: fullTenant?.id,
+                },
+              },
+            ],
+          },
+          {
+            and: [
+              {
+                username: {
+                  equals: username,
+                },
+              },
+              {
+                'tenants.tenant': {
+                  equals: fullTenant?.id,
+                },
+              },
+            ],
+          },
+        ],
+      },
+    })
+
+    if (foundUser?.totalDocs > 0) {
+      try {
+        const loginAttempt = await req.payload.login({
+          collection: 'users',
+          data: {
+            email: foundUser?.docs[0]?.email || '',
+            password,
+          },
+          req,
+        })
+
+        if (loginAttempt?.token) {
+          const collection: Collection = (req.payload.collections as { [key: string]: Collection })[
+            'users'
+          ]!
+          const cookie = generatePayloadCookie({
+            collectionAuthConfig: collection.config.auth,
+            cookiePrefix: req.payload.config.cookiePrefix,
+            token: loginAttempt.token,
+          })
+
+          return Response.json(loginAttempt, {
+            headers: headersWithCors({
+              headers: new Headers({
+                'Set-Cookie': cookie,
+              }),
+              req,
+            }),
+            status: 200,
+          })
+        }
+
+        throw new APIError(
+          'Unable to login with the provided username and password.',
+          400,
+          null,
+          true,
+        )
+      } catch (e) {
+        throw new APIError(
+          'Unable to login with the provided username and password.',
+          400,
+          null,
+          true,
+        )
+      }
+    }
+
+    throw new APIError('Unable to login with the provided username and password.', 400, null, true)
+  },
+  method: 'post',
+  path: '/external-users/login',
+}
diff --git a/src/collections/Users/hooks/ensureUniqueUsername.ts b/src/collections/Users/hooks/ensureUniqueUsername.ts
new file mode 100644
index 0000000..ab51e4d
--- /dev/null
+++ b/src/collections/Users/hooks/ensureUniqueUsername.ts
@@ -0,0 +1,76 @@
+import type { FieldHook, Where } from 'payload'
+
+import { ValidationError } from 'payload'
+
+import { extractID } from '@/utilities/extractID'
+import { getTenantFromCookie } from '@payloadcms/plugin-multi-tenant/utilities'
+import { getCollectionIDType } from '@/utilities/getCollectionIDType'
+import { getUserTenantIDs } from '@/utilities/getUserTenantIds'
+
+export const ensureUniqueUsername: FieldHook = async ({ data, originalDoc, req, value }) => {
+  // if value is unchanged, skip validation
+  if (originalDoc.username === value) {
+    return value
+  }
+
+  const constraints: Where[] = [
+    {
+      username: {
+        equals: value,
+      },
+    },
+  ]
+
+  const selectedTenant = getTenantFromCookie(
+    req.headers,
+    getCollectionIDType({ payload: req.payload, collectionSlug: 'tenants' }),
+  )
+
+  if (selectedTenant) {
+    constraints.push({
+      'tenants.tenant': {
+        equals: selectedTenant,
+      },
+    })
+  }
+
+  const findDuplicateUsers = await req.payload.find({
+    collection: 'users',
+    where: {
+      and: constraints,
+    },
+  })
+
+  if (findDuplicateUsers.docs.length > 0 && req.user) {
+    const tenantIDs = getUserTenantIDs(req.user)
+    // if the user is an admin or has access to more than 1 tenant
+    // provide a more specific error message
+    if (req.user.roles?.includes('super-admin') || tenantIDs.length > 1) {
+      const attemptedTenantChange = await req.payload.findByID({
+        // @ts-ignore - selectedTenant will match DB ID type
+        id: selectedTenant,
+        collection: 'tenants',
+      })
+
+      throw new ValidationError({
+        errors: [
+          {
+            message: `The "${attemptedTenantChange.name}" tenant already has a user with the username "${value}". Usernames must be unique per tenant.`,
+            path: 'username',
+          },
+        ],
+      })
+    }
+
+    throw new ValidationError({
+      errors: [
+        {
+          message: `A user with the username ${value} already exists. Usernames must be unique per tenant.`,
+          path: 'username',
+        },
+      ],
+    })
+  }
+
+  return value
+}
diff --git a/src/collections/Users/hooks/setCookieBasedOnDomain.ts b/src/collections/Users/hooks/setCookieBasedOnDomain.ts
new file mode 100644
index 0000000..fe01891
--- /dev/null
+++ b/src/collections/Users/hooks/setCookieBasedOnDomain.ts
@@ -0,0 +1,39 @@
+import type { CollectionAfterLoginHook } from 'payload'
+
+import { mergeHeaders, generateCookie, getCookieExpiration } from 'payload'
+
+export const setCookieBasedOnDomain: CollectionAfterLoginHook = async ({ req, user }) => {
+  const relatedOrg = await req.payload.find({
+    collection: 'tenants',
+    depth: 0,
+    limit: 1,
+    where: {
+      domain: {
+        equals: req.headers.get('host'),
+      },
+    },
+  })
+
+  // If a matching tenant is found, set the 'payload-tenant' cookie
+  if (relatedOrg && relatedOrg.docs.length > 0) {
+    const tenantCookie = generateCookie({
+      name: 'payload-tenant',
+      expires: getCookieExpiration({ seconds: 7200 }),
+      path: '/',
+      returnCookieAsObject: false,
+      value: String(relatedOrg.docs[0].id),
+    })
+
+    // Merge existing responseHeaders with the new Set-Cookie header
+    const newHeaders = new Headers({
+      'Set-Cookie': tenantCookie as string,
+    })
+
+    // Ensure you merge existing response headers if they already exist
+    req.responseHeaders = req.responseHeaders
+      ? mergeHeaders(req.responseHeaders, newHeaders)
+      : newHeaders
+  }
+
+  return user
+}
diff --git a/src/collections/Users/index.ts b/src/collections/Users/index.ts
index 988a2b6..2e1bed3 100644
--- a/src/collections/Users/index.ts
+++ b/src/collections/Users/index.ts
@@ -1,7 +1,12 @@
 import type { CollectionConfig } from 'payload'
 
-import { authenticated } from '../../access/authenticated'
-import { isSuperAdmin } from '@/access/admin'
+import { createAccess } from './access/create'
+import { readAccess } from './access/read'
+import { updateAndDeleteAccess } from './access/updateAndDelete'
+import { externalUsersLogin } from './endpoints/externalUsersLogin'
+import { ensureUniqueUsername } from './hooks/ensureUniqueUsername'
+import { isSuperAdmin } from '@/access/isSuperAdmin'
+import { setCookieBasedOnDomain } from './hooks/setCookieBasedOnDomain'
 import { tenantsArrayField } from '@payloadcms/plugin-multi-tenant/fields'
 
 export enum UserAccessLevel {
@@ -35,17 +40,17 @@ const defaultTenantArrayField = tenantsArrayField({
 export const Users: CollectionConfig = {
   slug: 'users',
   access: {
-    admin: authenticated,
-    create: authenticated,
-    delete: authenticated,
-    read: authenticated,
-    update: authenticated,
+    create: createAccess,
+    delete: updateAndDeleteAccess,
+    read: readAccess,
+    update: updateAndDeleteAccess,
   },
   admin: {
     defaultColumns: ['name', 'email'],
     useAsTitle: 'username',
   },
   auth: true,
+  endpoints: [externalUsersLogin],
   fields: [
     {
       admin: {
@@ -56,18 +61,18 @@ export const Users: CollectionConfig = {
       defaultValue: ['guest'],
       hasMany: true,
       options: ['full-access', 'super-admin', 'user', 'guest'],
-      //     access: {
-      //       update: ({ req }) => {
-      //         return isSuperAdmin({req})
-      //       },
-      //     },
+      access: {
+        update: ({ req }) => {
+          return isSuperAdmin(req.user)
+        },
+      },
     },
     {
       name: 'username',
       type: 'text',
-      //      hooks: {
-      //        beforeValidate: [ensureUniqueUsername],
-      //      },
+      hooks: {
+        beforeValidate: [ensureUniqueUsername],
+      },
       index: true,
     },
     {
@@ -85,4 +90,7 @@ export const Users: CollectionConfig = {
     },
   ],
   timestamps: true,
+  hooks: {
+    afterLogin: [setCookieBasedOnDomain],
+  },
 }
diff --git a/src/utilities/extractID.ts b/src/utilities/extractID.ts
new file mode 100644
index 0000000..fe97a16
--- /dev/null
+++ b/src/utilities/extractID.ts
@@ -0,0 +1,10 @@
+import { Config } from '@/payload-types'
+import type { CollectionSlug } from 'payload'
+
+export const extractID = <T extends Config['collections'][CollectionSlug]>(
+  objectOrID: T | T['id'],
+): T['id'] => {
+  if (objectOrID && typeof objectOrID === 'object') return objectOrID.id
+
+  return objectOrID
+}
diff --git a/src/utilities/getCollectionIDType.ts b/src/utilities/getCollectionIDType.ts
new file mode 100644
index 0000000..02ed72f
--- /dev/null
+++ b/src/utilities/getCollectionIDType.ts
@@ -0,0 +1,9 @@
+import type { CollectionSlug, Payload } from 'payload'
+
+type Args = {
+  collectionSlug: CollectionSlug
+  payload: Payload
+}
+export const getCollectionIDType = ({ collectionSlug, payload }: Args): 'number' | 'text' => {
+  return payload.collections[collectionSlug]?.customIDType ?? payload.db.defaultIDType
+}
diff --git a/src/utilities/getUserTenantIds.ts b/src/utilities/getUserTenantIds.ts
new file mode 100644
index 0000000..a2e7b48
--- /dev/null
+++ b/src/utilities/getUserTenantIds.ts
@@ -0,0 +1,31 @@
+import type { Tenant, User } from '@/payload-types'
+import { extractID } from './extractID'
+
+/**
+ * Returns array of all tenant IDs assigned to a user
+ *
+ * @param user - User object with tenants field
+ * @param role - Optional role to filter by
+ */
+export const getUserTenantIDs = (
+  user: null | User,
+  role?: NonNullable<User['tenants']>[number]['roles'][number],
+): Tenant['id'][] => {
+  if (!user) {
+    return []
+  }
+
+  return (
+    user?.tenants?.reduce<Tenant['id'][]>((acc, { roles, tenant }) => {
+      if (role && !roles.includes(role)) {
+        return acc
+      }
+
+      if (tenant) {
+        acc.push(extractID(tenant))
+      }
+
+      return acc
+    }, []) || []
+  )
+}