Phase 1, Phase I or Phase One may refer to:
Media and music Marvel Cinematic Universe: Phase One, six American superhero films from 2008–2012 Phase One (Art Ensemble of Chicago album), 1971 Phase 1 (Saga album), 1998 Phase One, renamed Bloodwork (film), a 2012 American-Canadian thriller PhaseOne, Australian DJ and electronic music producer
Other Phase I clinical trials, the first of the phases of clinical research Canadian Phase I, a powered parachute design Phase I metabolism, Phase I reaction in drug metabolism Phase I environmental site assessment, a report prepared for a real estate holding which identifies potential or existing environmental contamination liabilities Phase 1 (bar), a lesbian bar and nightclub at 525 8th Street, Southeast in Washington, D.C Phase One (company), a Danish camera equipment company Phase 1 metro station Phase One Media Pro Phase One Endurance
See also Phase (disambiguation)