BRUSSELS—Antitrust authorities in Europe are examining Apple Inc.’s agreements with record labels as the California company prepares to launch a subscription music-streaming service that analysts say could become the biggest in the world, overtaking players such as Spotify AB.

The European Commission, the region’s top competition regulator, has sent questionnaires to several record labels seeking information about their dealings with Apple, two people familiar with the matter said Thursday. The regulator is interested in the...