Yes, an Apple Watch can play radio without the iPhone. A standalone watch app streams over the watch's own Wi-Fi or cellular connection, so the phone can stay at home, and the audio goes to Bluetooth headphones. What follows is what that needs, and what it costs in battery.
Does the Apple Watch have an FM radio?
No. No Apple Watch has ever included an FM tuner, and there is no hidden chip to unlock, which is the same story as on the phone: the iPhone has no FM radio either. Everything you can listen to on the watch arrives over the internet.
That trade is not all bad. FM would have given you the transmitters within range of your wrist; internet radio gives you every station in the world that streams, which on a watch is the difference between a handful of local signals and 55,000 stations.
Wi-Fi, cellular, or the iPhone nearby
Three situations, three answers. With the iPhone nearby, the watch can lean on the phone's connection and everything simply works. With the phone away and a known Wi-Fi network in range, the watch connects by itself, which covers home, the office and the gym. With the phone away and no Wi-Fi, a cellular watch keeps streaming on its own plan, while a GPS-only watch has nothing to connect through and stays silent.
This is the single thing worth checking before a run: leaving the phone behind only works if the watch has cellular or the route stays inside Wi-Fi.
What standalone actually means
Most watch apps are remote controls: they need the iPhone nearby and merely steer it. A standalone app streams on the watch itself. Macdio's watch app is fully standalone: it connects to the station over the watch's own Wi-Fi or cellular, so the phone can be in another city. The full feature list is on Macdio for Apple Watch.
What you need
A connection
Known Wi-Fi, or cellular on LTE watch models. The watch handles the rest.
Bluetooth audio
AirPods or any Bluetooth headphones. watchOS sends streamed audio to Bluetooth, not the built-in speaker.
Your stations
Favorites sync from your other devices through iCloud, and the watch has its own library view and search.
Battery honesty
Streaming over LTE is the heaviest thing a watch radio can do; expect a noticeably faster drain than on Wi-Fi. For a long session, Wi-Fi plus a lower-bitrate station is the economical combination. On the data side, a 128 kbps stream costs roughly 58 MB an hour, so an hour of listening is a rounding error next to what a podcast download or a maps route uses. On the phone side, Macdio for iPhone and internet radio on CarPlay stream the same stations without the battery limits.
Frequently asked questions
Can Apple Watch play radio without the iPhone?
Do I need headphones?
Is the watch app a separate purchase?
Does it work on Apple Watch SE?
Can I listen while running without the phone?
Do my stations sync from the iPhone?
Can I record radio on the watch?
Ready to try it?
Get Macdio on the App Store and the watch app installs alongside the iPhone app.