Cellular Apple Watch

In 2017, Apple announced Apple Watch Series 3, available in two models: cellular Apple Watches being marketed as GPS+Cellular, and Watches lacking cellular capabilities marketed as GPS. Until 2020, all Apple Watches required, during initial setup, that the owner have an iPhone to complete the setup of the Watch.

Starting 2020, Apple introduced an exception that allows cellular models (GPS+cellular models) to be purchased and used by someone who doesn't own an iPhone. The Watch owner must be part of a Family Group, and their family manager must own an iPhone. Wi-Fi watches (GPS models) are not eligible to be set up for a family member, and some apps are disabled on a family setup watch.

If the watch is to be used for offline-only/Wi-Fi only purposes, then the family iPhone does not need to have an active carrier plan. Apple Watch Series 9 and newer support offline Siri.

In most countries, setting up a cellular plan on a watch requires that the Watch carrier be the same as the family iPhone carrier. The countries where Apple does not require watches to be "carrier paired" are: US, UK, France, Germany, Poland, Spain and Switzerland. In these countries, the watch can have not only its own phone number, but also its own independent cellular plan directly with Truphone (available in six countries), Telekom (in Germany), or Sunrise or Swisscom (in Switzerland).

Stand alone cellwatches
The following models are capable of "family setup" since 2020, provided the model is GPS+cellular (GPS-only models are not permitted to use family setup):

Note that international emergency calling is not available on Series 4.

Truphone
Truphone was selected by Apple as the first multi-country carrier to offer cellular plans for standalone Apple Watches. Truphone offers this service in the following countries:
 * United States
 * United Kingdom
 * France
 * Germany
 * Poland
 * Spain
 * Australia (family iPhone must also be on Truphone)

Local Carriers
Bold indicates that the carrier allows the watch on their network even if the associated iPhone is not on that carrier.

Americas:
 * Canada: Bell, Telus
 * United States: AT&T, Verizon, T-Mobile, US Cellular, C Spire

Europe
 * United Kingdom: EE
 * Norway: Telia
 * Germany: Telekom
 * Switzerland: Sunrise, Swisscom
 * Spain: Movistar

Asia and Middle East
 * Bahrain: Batelco
 * Japan: au
 * Thailand: AIS, dtac, TrueMove
 * Singapore: Starhub
 * Taiwan: Chungwa, Taiwan Mobile, FarEasTone
 * Hong Kong: 1O1O, csl, SmarTone
 * China: China Unicom, China Telecom (in 7 cities)