With Apple Watch 4, can I make phone calls without an iPhone? I'd like to use Apple Watch Series 4 as a standalone device to make phone calls.

On an Apple Watch Series 4 Cellular, can I make a phone call via cellular network without my iPhone, which I'd like to leave at home, connected to it via Bluetooth or WiFi?

And, can I additionally make phone calls via a Bluetooth headset which connects directly to the Apple Watch 4?
An Apple Watch Series 4 (along with Series 3) with support for Cellular can make a phone call without an iPhone but will need to be paired with it. Apple Watch Cellular comes with a build-in eSIM. It needs to be paired with the SIM card in your iPhone.


How to use your Apple Watch without your iPhone nearby


Apple Watch Series 4 is typically expected to support all the phone call/cellular features of Series 3.

Note: Having an iPhone is a prerequisite for using an(any) Apple Watch. Thus, it's not possible to use an Apple Watch (any generation), without owning an iPhone.