Does Ultra 3 watch require a SIM card?

No. Apple Watches don't use physical SIM cards. They include digital eSim support but that does not need to be enabled or have an active plan. You can use the Apple Watch without cell service while near the paired iPhone.

And some features are available when away from the paired iPhone, but connected to Wi-Fi

click here ➜ Use your Apple Watch without your iPhone nearby - Apple Support

Paired with an iPhone, it can share the phone service from the iPhone through the eSim.

click here ➜ Set up cellular on Apple Watch - Apple Support

La Chevre wrote:

I have an ultra 3 watch and wondered do I need a SIM card .?

If, however, you’re asking whether you need a cellular plan (and eSIM) to use an Apple Watch, no. You don’t.

The Apple Watch will operate via the paired iPhone when within range, and will use known Wi-Fi networks when out of range.

An Apple Watch cellular plan adds the ability to use the cellular network when out of range of the paired iPhone, and out of range of a known Wi-Fi network.

When an Apple Watch with cellular is within range of the paired iPhone, it’ll still prefer to communicate via the paired iPhone and its comparatively far larger power reserves.

Outside of the added cellular communications path, an Apple Watch operates the same with or without that plan.

I might add a personal comment, unless you plan on wandering about having left your iphone at home, and being in contact, it really isnt worth the £$10 a month for the privilege, or the battery drain.

As Tim Cook once said, who goes out without their iPhone?

Hello~ Have a look at this previous post by *FoxFifth* by clicking on the link be…

https://discussions.apple.com/thread/255623852?sortBy=oldest_first

~Katana-San~

LD150 wrote:

I might add a personal comment, unless you plan on wandering about having left your iphone at home, and being in contact, it really isnt worth the £$10 a month for the privilege, or the battery drain.

As Tim Cook once said, who goes out without their iPhone?

Calculations and environments and expectations differ.

I swim. iPhone doesn’t.

Watch also serves as a backup, should the phone become unavailable.

And without any doubt, Tim has cellular.

LD150 wrote:

I might add a personal comment, unless you plan on wandering about having left your iphone at home, and being in contact, it really isnt worth the £$10 a month for the privilege, or the battery drain.

As Tim Cook once said, who goes out without their iPhone?

It's lovely to be able to go for a walk (used to be a run!) without carrying my phone, yet still be able to listen to music. And then there was the time I left my phone at work and had to get in touch with the people I was meeting for dinner. Could I survive without it? Absolutely. Do I find it nice to have? Also, absolutely.

OK but workouts can be recorded on Watch without a nearby iphone.

Just saying personally I would not pay £10 pm for a cellular plan AND upgrade my £10 pm on contract MVNO phone plan to a £30 a month main provider 2 yr contract just because MVNOs are 'discouraged' from providing Watch cellular.

However I guess if people are barmy enough to splash out £800 on a wearable, they may have the spare cash to feed it.