diff --git a/apps/web/app/api/customer-card/route.ts b/apps/web/app/api/customer-card/route.ts
index 4f50541985..e934b10053 100644
--- a/apps/web/app/api/customer-card/route.ts
+++ b/apps/web/app/api/customer-card/route.ts
@@ -7,6 +7,7 @@ import { z } from "zod";
 
 import dayjs from "@calcom/dayjs";
 import { UserRepository } from "@calcom/lib/server/repository/user";
+import { timeZoneSchema } from "@calcom/lib/dayjs/timeZone.schema";
 import { userMetadata } from "@calcom/prisma/zod-utils";
 
 import { CardComponent } from "@lib/plain/card-components";
@@ -443,7 +444,7 @@ const inputSchema = z.object({
     name: z.string().optional(),
     email: z.string().email(),
     username: z.string().optional(),
-    timeZone: z.string().optional(),
+    timeZone: timeZoneSchema.optional(),
     emailVerified: z.boolean().optional(),
     identityProvider: z.string().optional(),
     twoFactorEnabled: z.boolean().optional(),
diff --git a/packages/features/users/components/UserTable/EditSheet/EditUserForm.tsx b/packages/features/users/components/UserTable/EditSheet/EditUserForm.tsx
index 942919ef96..b5a3f5073f 100644
--- a/packages/features/users/components/UserTable/EditSheet/EditUserForm.tsx
+++ b/packages/features/users/components/UserTable/EditSheet/EditUserForm.tsx
@@ -6,6 +6,7 @@ import { Controller, useForm, useFormContext } from "react-hook-form";
 import { z } from "zod";
 
 import { TimezoneSelect } from "@calcom/features/components/timezone-select";
+import { timeZoneSchema } from "@calcom/lib/dayjs/timeZone.schema";
 import { emailSchema } from "@calcom/lib/emailSchema";
 import { useLocale } from "@calcom/lib/hooks/useLocale";
 import { MembershipRole } from "@calcom/prisma/enums";
@@ -58,7 +59,7 @@ const editSchema = z.object({
   avatar: z.string(),
   bio: z.string(),
   role: z.enum([MembershipRole.MEMBER, MembershipRole.ADMIN, MembershipRole.OWNER]),
-  timeZone: z.string(),
+  timeZone: timeZoneSchema,
   // schedules: z.array(z.string()),
   // teams: z.array(z.string()),
   attributes: z.array(attributeSchema).optional(),
diff --git a/packages/lib/dayjs/timeZone.schema.ts b/packages/lib/dayjs/timeZone.schema.ts
new file mode 100644
index 0000000000..920ad9c225
--- /dev/null
+++ b/packages/lib/dayjs/timeZone.schema.ts
@@ -0,0 +1,8 @@
+import { z } from "zod";
+
+import { isSupportedTimeZone } from "./index";
+
+// Schema for validating IANA timezone strings compatible with Intl.DateTimeFormat
+export const timeZoneSchema = z.string().refine((timeZone) => isSupportedTimeZone(timeZone), {
+  message: "Invalid timezone. Must be a valid IANA timezone string.",
+});
diff --git a/packages/prisma/zod/custom/booking.ts b/packages/prisma/zod/custom/booking.ts
index 45c0d44070..1e51576761 100644
--- a/packages/prisma/zod/custom/booking.ts
+++ b/packages/prisma/zod/custom/booking.ts
@@ -1,6 +1,6 @@
 // `responses` is merged with it during handleNewBooking call because `responses` schema is dynamic and depends on eventType
 import z, { ZodNullable, ZodObject, ZodOptional } from "zod";
-import { isSupportedTimeZone } from "@calcom/lib/dayjs";
+import { timeZoneSchema } from "@calcom/lib/dayjs/timeZone.schema";
 // TODO: Move this out of here. Importing from app-store is a circular package dependency.
 import { routingFormResponseInDbSchema } from "@calcom/app-store/routing-forms/zod";
 
@@ -12,7 +12,7 @@ export const bookingCreateBodySchema = z.object({
   recurringEventId: z.string().optional(),
   rescheduledBy: z.string().email({ message: "Invalid email" }).optional(),
   start: z.string(),
-  timeZone: z.string().refine((value: string) => isSupportedTimeZone(value), { message: "Invalid timezone" }),
+  timeZone: timeZoneSchema,
   user: z.union([z.string(), z.array(z.string())]).optional(),
   language: z.string(),
   bookingUid: z.string().optional(),
diff --git a/packages/trpc/server/routers/viewer/availability/schedule/update.schema.ts b/packages/trpc/server/routers/viewer/availability/schedule/update.schema.ts
index e37588842c..7e8b6bfd23 100644
--- a/packages/trpc/server/routers/viewer/availability/schedule/update.schema.ts
+++ b/packages/trpc/server/routers/viewer/availability/schedule/update.schema.ts
@@ -1,8 +1,10 @@
 import { z } from "zod";
 
+import { timeZoneSchema } from "@calcom/lib/dayjs/timeZone.schema";
+
 export const ZUpdateInputSchema = z.object({
   scheduleId: z.number(),
-  timeZone: z.string().optional(),
+  timeZone: timeZoneSchema.optional(),
   name: z.string().optional(),
   isDefault: z.boolean().optional(),
   schedule: z
diff --git a/packages/trpc/server/routers/viewer/me/updateProfile.schema.ts b/packages/trpc/server/routers/viewer/me/updateProfile.schema.ts
index ab9a4a7a20..c3c75b1b62 100644
--- a/packages/trpc/server/routers/viewer/me/updateProfile.schema.ts
+++ b/packages/trpc/server/routers/viewer/me/updateProfile.schema.ts
@@ -1,6 +1,7 @@
 import { z } from "zod";
 
 import { FULL_NAME_LENGTH_MAX_LIMIT } from "@calcom/lib/constants";
+import { timeZoneSchema } from "@calcom/lib/dayjs/timeZone.schema";
 import { bookerLayouts, userMetadata } from "@calcom/prisma/zod-utils";
 
 export const updateUserMetadataAllowedKeys = z.object({
@@ -14,7 +15,7 @@ export const ZUpdateProfileInputSchema = z.object({
   email: z.string().optional(),
   bio: z.string().optional(),
   avatarUrl: z.string().nullable().optional(),
-  timeZone: z.string().optional(),
+  timeZone: timeZoneSchema.optional(),
   weekStart: z.string().optional(),
   hideBranding: z.boolean().optional(),
   allowDynamicBooking: z.boolean().optional(),
@@ -33,7 +34,7 @@ export const ZUpdateProfileInputSchema = z.object({
     .array(
       z.object({
         id: z.number().optional(),
-        timeZone: z.string(),
+        timeZone: timeZoneSchema,
         endDate: z.date().optional(),
         startDate: z.date(),
       })
diff --git a/packages/trpc/server/routers/viewer/organizations/update.schema.ts b/packages/trpc/server/routers/viewer/organizations/update.schema.ts
index 42434e1fdd..b541771bd7 100644
--- a/packages/trpc/server/routers/viewer/organizations/update.schema.ts
+++ b/packages/trpc/server/routers/viewer/organizations/update.schema.ts
@@ -1,5 +1,6 @@
 import { z } from "zod";
 
+import { timeZoneSchema } from "@calcom/lib/dayjs/timeZone.schema";
 import { teamMetadataSchema } from "@calcom/prisma/zod-utils";
 
 export const ZUpdateInputSchema = z.object({
@@ -24,7 +25,7 @@ export const ZUpdateInputSchema = z.object({
   brandColor: z.string().optional(),
   darkBrandColor: z.string().optional(),
   theme: z.string().optional().nullable(),
-  timeZone: z.string().optional(),
+  timeZone: timeZoneSchema.optional(),
   weekStart: z.string().optional(),
   timeFormat: z.number().optional(),
   metadata: teamMetadataSchema.unwrap().optional(),
diff --git a/packages/trpc/server/routers/viewer/organizations/updateUser.schema.ts b/packages/trpc/server/routers/viewer/organizations/updateUser.schema.ts
index 04717ed112..2084e7c228 100644
--- a/packages/trpc/server/routers/viewer/organizations/updateUser.schema.ts
+++ b/packages/trpc/server/routers/viewer/organizations/updateUser.schema.ts
@@ -1,5 +1,7 @@
 import { z } from "zod";
 
+import { timeZoneSchema } from "@calcom/lib/dayjs/timeZone.schema";
+
 import { assignUserToAttributeSchema } from "../attributes/assignUserToAttribute.schema";
 
 export const ZUpdateUserInputSchema = z.object({
@@ -10,7 +12,7 @@ export const ZUpdateUserInputSchema = z.object({
   email: z.string().optional(),
   avatar: z.string().optional(),
   role: z.enum(["ADMIN", "MEMBER", "OWNER"]),
-  timeZone: z.string(),
+  timeZone: timeZoneSchema,
   attributeOptions: assignUserToAttributeSchema.optional(),
 });
 
diff --git a/packages/trpc/server/routers/viewer/slots/types.ts b/packages/trpc/server/routers/viewer/slots/types.ts
index f660b09a49..cc81e6525e 100644
--- a/packages/trpc/server/routers/viewer/slots/types.ts
+++ b/packages/trpc/server/routers/viewer/slots/types.ts
@@ -1,6 +1,8 @@
 import type { IncomingMessage } from "http";
 import { z } from "zod";
 
+import { timeZoneSchema } from "@calcom/lib/dayjs/timeZone.schema";
+
 export const getScheduleSchema = z
   .object({
     // startTime ISOString
@@ -12,7 +14,7 @@ export const getScheduleSchema = z
     // Event type slug
     eventTypeSlug: z.string().optional(),
     // invitee timezone
-    timeZone: z.string().optional(),
+    timeZone: timeZoneSchema.optional(),
     // or list of users (for dynamic events)
     usernameList: z.array(z.string()).min(1).optional(),
     debug: z.boolean().optional(),
diff --git a/packages/trpc/server/routers/viewer/teams/getMemberAvailability.schema.ts b/packages/trpc/server/routers/viewer/teams/getMemberAvailability.schema.ts
index 07b62c1296..8cc05ab10c 100644
--- a/packages/trpc/server/routers/viewer/teams/getMemberAvailability.schema.ts
+++ b/packages/trpc/server/routers/viewer/teams/getMemberAvailability.schema.ts
@@ -1,9 +1,11 @@
 import { z } from "zod";
 
+import { timeZoneSchema } from "@calcom/lib/dayjs/timeZone.schema";
+
 export const ZGetMemberAvailabilityInputSchema = z.object({
   teamId: z.number(),
   memberId: z.number(),
-  timezone: z.string(),
+  timezone: timeZoneSchema,
   dateFrom: z.string(),
   dateTo: z.string(),
 });