Hypothesis is a studio album by the Greek electronic composer Vangelis, unofficially released in 1978.

In May 1971 Vangelis had played several sessions in London's Marquee Studios, joined for some of them by violinist Michel Ripoche, bass guitarist Brian Odgers (called Odger on the sleeve) and drummer Tony Oxley, the rhythm section of the famous Extrapolation recording released by John McLaughlin.

Two albums' worth of material had resulted from these sessions, but were unfinished and not intended for release.

He said greed was the motivation for releasing the sub-par albums: "I don't agree with that music at all.

The cover artwork for Hypothesis is by Angus McKie, and is merely a "borrowed" illustration he drew for a series of novels by SF author Brian Stableford, featuring the spacecraft Hooded Swan, mentioned in the books.