In a joint press conference today, founders of the two companies said they were "super-excited" about launching the service, which premieres on Friday.
Although they wouldn't give much information about the terms of the tie-up, Uber founder Travis Kalanick described it as a "mutual win-win" - it's likely, for example, that the two companies will cross-promote.
"It's the first time we've personalised the experience inside the car," said Kalanick, while Spotify founder Daniel Ek described it as "Nirvana" for music-lovers. (Or a "Beyonce". Depends what you're into, we guess...).
The functionality will be within the Uber app, rather than Spotify, and will apply to all Uber's products apart from UberPool and UberTaxi. It also relies on drivers having connected the phones they use for Uber to the audio system in their cars - although Kalanick said the response from drivers had been positive.
But how will drivers react to music they can't stand? Drivers will have control over the volume of the music, which is good news - although Kalanick said Uber will keep an eye on "tension points".
The service will launch in 10 cities, including (naturally) London, Stockholm and Nashville, with parties in each of the cities that will be "pretty wild".