diff --git a/ui/litellm-dashboard/src/components/CreateUserButton.integration.test.tsx b/ui/litellm-dashboard/src/components/CreateUserButton.integration.test.tsx
new file mode 100644
index 00000000000..e89211596f3
--- /dev/null
+++ b/ui/litellm-dashboard/src/components/CreateUserButton.integration.test.tsx
@@ -0,0 +1,111 @@
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { fireEvent, render, screen, waitFor, within } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { CreateUserButton } from "./CreateUserButton";
+
+const createUser = vi.fn<(body: Record<string, unknown>) => Response>();
+const unexpectedRequest = vi.fn((path: string) =>
+  Response.json({ error: `Unexpected request ${path}` }, { status: 500 }),
+);
+
+beforeEach(() => {
+  unexpectedRequest.mockClear();
+  createUser.mockReset();
+  createUser.mockImplementation((body) => Response.json({ user_id: body.user_id ?? "generated-id" }));
+  vi.stubGlobal(
+    "fetch",
+    vi.fn(async (input: RequestInfo | URL, init?: RequestInit) => {
+      const path = new URL(input instanceof Request ? input.url : String(input), "http://localhost").pathname;
+      if (path === "/user/new") return createUser(JSON.parse(String(init?.body)));
+      if (path === "/models") return Response.json({ data: [] });
+      if (path === "/sso/get/ui_settings") return Response.json({ SSO_ENABLED: true });
+      if (path === "/v2/team/list") return Response.json({ teams: [], total: 0, total_pages: 0 });
+      return unexpectedRequest(path);
+    }),
+  );
+});
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+  expect(unexpectedRequest).not.toHaveBeenCalled();
+});
+
+const renderForm = (isEmbedded: boolean, onUserCreated = vi.fn()) => {
+  const client = new QueryClient({ defaultOptions: { queries: { retry: false, gcTime: 0 } } });
+  render(
+    <QueryClientProvider client={client}>
+      <CreateUserButton
+        userID="admin"
+        accessToken="test-token"
+        possibleUIRoles={null}
+        isEmbedded={isEmbedded}
+        onUserCreated={onUserCreated}
+      />
+    </QueryClientProvider>,
+  );
+  return onUserCreated;
+};
+
+describe("custom User ID invitation", () => {
+  it.each([true, false])("sends the custom ID from the form (embedded=%s)", async (embedded) => {
+    const user = userEvent.setup();
+    const onCreated = renderForm(embedded);
+    if (!embedded) await user.click(screen.getByRole("button", { name: "+ Invite User" }));
+    await user.click(screen.getByRole("checkbox", { name: "Supply custom User ID" }));
+    fireEvent.change(screen.getByRole("textbox", { name: "User ID", exact: true }), {
+      target: { value: "  employee-42  " },
+    });
+    fireEvent.change(screen.getByRole("textbox", { name: "User Email" }), {
+      target: { value: "employee@example.test" },
+    });
+    await user.click(screen.getByRole("button", { name: embedded ? "Create User" : "Invite User", exact: true }));
+    await waitFor(() =>
+      expect(createUser).toHaveBeenCalledWith(
+        expect.objectContaining({
+          user_id: "employee-42",
+          user_email: "employee@example.test",
+          auto_create_key: false,
+        }),
+      ),
+    );
+    expect(createUser.mock.calls[0][0]).not.toHaveProperty("supply_user_id");
+    if (embedded) {
+      await waitFor(() => expect(onCreated).toHaveBeenCalledWith("employee-42"));
+      expect(screen.getByRole("checkbox", { name: "Supply custom User ID" })).not.toBeChecked();
+      expect(screen.queryByRole("textbox", { name: "User ID", exact: true })).not.toBeInTheDocument();
+    }
+  });
+
+  it("blocks whitespace and clears the custom ID when automatic generation is selected", async () => {
+    const user = userEvent.setup();
+    renderForm(true);
+    await user.click(screen.getByRole("checkbox", { name: "Supply custom User ID" }));
+    fireEvent.change(screen.getByRole("textbox", { name: "User ID", exact: true }), { target: { value: "   " } });
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+    expect(await screen.findByText("Enter a User ID")).toBeInTheDocument();
+    expect(createUser).not.toHaveBeenCalled();
+    fireEvent.change(screen.getByRole("textbox", { name: "User ID", exact: true }), {
+      target: { value: "discard-me" },
+    });
+    await user.click(screen.getByRole("checkbox", { name: "Supply custom User ID" }));
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+    await waitFor(() => expect(createUser).toHaveBeenCalledWith(expect.objectContaining({ user_id: null })));
+    expect(createUser.mock.calls[0][0]).not.toHaveProperty("supply_user_id");
+  });
+
+  it("discards a custom ID when an invitation is cancelled", async () => {
+    const user = userEvent.setup();
+    renderForm(false);
+    await user.click(screen.getByRole("button", { name: "+ Invite User" }));
+    await user.click(screen.getByRole("checkbox", { name: "Supply custom User ID" }));
+    fireEvent.change(screen.getByRole("textbox", { name: "User ID", exact: true }), { target: { value: "cancelled" } });
+    await user.click(
+      within(screen.getByRole("dialog", { name: "Invite User" })).getByRole("button", { name: "Close" }),
+    );
+    await user.click(screen.getByRole("button", { name: "+ Invite User" }));
+    expect(screen.getByRole("checkbox", { name: "Supply custom User ID" })).not.toBeChecked();
+    await user.click(screen.getByRole("checkbox", { name: "Supply custom User ID" }));
+    expect(screen.getByRole("textbox", { name: "User ID", exact: true })).toHaveValue("");
+  });
+});
diff --git a/ui/litellm-dashboard/src/components/CreateUserButton.test.tsx b/ui/litellm-dashboard/src/components/CreateUserButton.test.tsx
index 94b3726ede0..d04272cecd3 100644
--- a/ui/litellm-dashboard/src/components/CreateUserButton.test.tsx
+++ b/ui/litellm-dashboard/src/components/CreateUserButton.test.tsx
@@ -308,7 +308,7 @@ describe("CreateUserButton", () => {
 
     const dialog = screen.getByRole("dialog", { name: /invite user/i });
 
-    expectControlBesideLabel(within(dialog).getByRole("checkbox"));
+    expectControlBesideLabel(within(dialog).getByRole("checkbox", { name: "Send invitation email" }));
   });
 
   describe("organizations", () => {
diff --git a/ui/litellm-dashboard/src/components/CreateUserButton.tsx b/ui/litellm-dashboard/src/components/CreateUserButton.tsx
index 6fbe8f2d2bd..bf188d36716 100644
--- a/ui/litellm-dashboard/src/components/CreateUserButton.tsx
+++ b/ui/litellm-dashboard/src/components/CreateUserButton.tsx
@@ -14,7 +14,7 @@ import { Tooltip, TooltipContent, TooltipProvider, TooltipTrigger } from "@/comp
 import { Alert, AlertDescription, AlertTitle } from "@/components/shared/Alert";
 import { ChevronRight, CircleHelp, Info, UserPlus } from "lucide-react";
 import React, { useEffect, useState } from "react";
-import { useForm } from "react-hook-form";
+import { useForm, useWatch } from "react-hook-form";
 import { useTranslation } from "react-i18next";
 import TeamDropdown from "./common_components/team_dropdown";
 import { getModelDisplayName } from "./key_team_helpers/fetch_available_models_team_key";
@@ -58,6 +58,8 @@ interface UISettings {
 }
 
 interface CreateUserFormValues {
+  supply_user_id: boolean;
+  user_id?: string;
   user_email?: string;
   user_role: string;
   team_id?: string | null;
@@ -68,6 +70,8 @@ interface CreateUserFormValues {
 }
 
 const EMBEDDED_DEFAULTS: CreateUserFormValues = {
+  supply_user_id: false,
+  user_id: "",
   user_email: undefined,
   user_role: "internal_user_viewer",
   team_id: undefined,
@@ -76,6 +80,8 @@ const EMBEDDED_DEFAULTS: CreateUserFormValues = {
 };
 
 const STANDALONE_DEFAULTS: CreateUserFormValues = {
+  supply_user_id: false,
+  user_id: "",
   user_email: undefined,
   user_role: "internal_user_viewer",
   team_id: undefined,
@@ -95,11 +101,13 @@ const withoutCollapsedModels = (values: CreateUserFormValues, isPersonalKeyOpen:
   return rest;
 };
 
-const buildCreatePayload = (values: CreateUserFormValues): CreateUserFormValues & { organizations?: string[] } => {
+const buildCreatePayload = (values: CreateUserFormValues) => {
+  const { supply_user_id, user_id, ...fields } = values;
+  const apiValues = supply_user_id ? { ...fields, user_id: user_id?.trim() } : fields;
   const withModels =
     (!values.models || values.models.length === 0) && values.user_role !== "proxy_admin"
-      ? { ...values, models: ["no-default-models"] }
-      : values;
+      ? { ...apiValues, models: ["no-default-models"] }
+      : apiValues;
   if (!withModels.organization_ids) {
     return withModels;
   }
@@ -163,6 +171,7 @@ export const CreateUserButton: React.FC<CreateuserProps> = ({
   const [uiSettings, setUISettings] = useState<UISettings | null>(null);
   const defaultValues = isEmbedded ? EMBEDDED_DEFAULTS : STANDALONE_DEFAULTS;
   const form = useForm<CreateUserFormValues>({ defaultValues });
+  const supplyUserId = useWatch({ control: form.control, name: "supply_user_id" });
   const [isModalVisible, setIsModalVisible] = useState(false);
   const [apiuser, setApiuser] = useState<boolean>(false);
   const [userModels, setUserModels] = useState<string[]>([]);
@@ -205,6 +214,14 @@ export const CreateUserButton: React.FC<CreateuserProps> = ({
   };
 
   const handleCreate = async (formValues: CreateUserFormValues) => {
+    if (formValues.supply_user_id && !formValues.user_id?.trim()) {
+      form.setError("user_id", { message: "Enter a User ID" }, { shouldFocus: true });
+      return;
+    }
+    if (formValues.supply_user_id && formValues.user_id?.includes("\u0000")) {
+      form.setError("user_id", { message: "User ID must not contain NUL characters" }, { shouldFocus: true });
+      return;
+    }
     try {
       toast.info(t("users.createUser.toasts.makingApiCall"));
       if (!isEmbedded) {
@@ -255,6 +272,34 @@ export const CreateUserButton: React.FC<CreateuserProps> = ({
     </FormField>
   );
 
+  const userIdField = (
+    <>
+      <FormField control={form.control} name="supply_user_id" label="Supply custom User ID" orientation="horizontal">
+        {({ id, value, onChange, onBlur }) => (
+          <Checkbox
+            id={id}
+            checked={value}
+            onCheckedChange={(checked) => {
+              onChange(checked);
+              form.resetField("user_id");
+            }}
+            onBlur={onBlur}
+          />
+        )}
+      </FormField>
+      {supplyUserId && (
+        <FormField
+          control={form.control}
+          name="user_id"
+          label="User ID"
+          description="A unique ID for this user. Leave the checkbox unchecked to generate one automatically."
+        >
+          {({ ref, value, ...control }) => <Input {...control} ref={ref} value={value ?? ""} />}
+        </FormField>
+      )}
+    </>
+  );
+
   const teamField = (
     <FormField
       control={form.control}
@@ -325,6 +370,7 @@ export const CreateUserButton: React.FC<CreateuserProps> = ({
           <EmailInvitationsNotice />
           <FieldGroup>
             {userEmailField}
+            {userIdField}
             {roleField(t("users.createUser.fields.userRole"))}
             {teamField}
             {metadataField}
@@ -357,6 +403,7 @@ export const CreateUserButton: React.FC<CreateuserProps> = ({
             <form onSubmit={form.handleSubmit(handleCreate)}>
               <FieldGroup>
                 {userEmailField}
+                {userIdField}
                 {roleField(
                   labelWithHint(t("users.createUser.fields.globalRole"), t("users.createUser.fields.globalRoleHint")),
                 )}
@@ -436,7 +483,7 @@ export const CreateUserButton: React.FC<CreateuserProps> = ({
                 </Collapsible>
               </FieldGroup>
 
-              <div className="mt-4 text-right">
+              <div className="sticky bottom-0 -mx-6 mt-4 -mb-6 flex justify-end border-t bg-popover px-6 py-4">
                 <Button type="submit">
                   <UserPlus />
                   {t("users.createUser.submitButton")}