The third season of the American television series Agents of S.H.I.E.L.D., which is based on the Marvel Comics organization S.H.I.E.L.D. (Strategic Homeland Intervention, Enforcement, and Logistics Division), revolves around the character of Phil Coulson and his team of S.H.I.E.L.D. agents and allies, who begin a secret mission to assemble a team of Inhumans to deal with new threats to the world, while others are also tracking down members of the group. It is set in the Marvel Cinematic Universe (MCU), sharing continuity with the films of the franchise. The first episode of the season premiered in Los Angeles on September 23, 2015, with the season, consisting of 22 episodes, airing on ABC beginning on September 29. It is produced by ABC Studios, Marvel Television, and Mutant Enemy Productions, with Jed Whedon, Maurissa Tancharoen, and Jeffrey Bell serving as showrunners.

A third season of Agents of S.H.I.E.L.D. was ordered in May 2015, with production beginning late that July. Alongside Clark Gregg, who reprises his role as Coulson from the film series, principal cast members Ming-Na Wen, Brett Dalton, Chloe Bennet, Iain De Caestecker, Elizabeth Henstridge, Nick Blood, and Adrianne Palicki return from previous seasons, as do Henry Simmons and Luke Mitchell, now promoted to series regulars from their status as recurring characters in season two. Other characters from previous MCU media, including the films, also appear. The season takes inspiration from the Secret Warriors comic series, which features a team of the same name, combining it with the Inhuman storyline introduced in the previous season. Glenn Hetrick created prosthetics for the less-human looking Inhumans, and Legacy Effects provided additional practical effects and props.

The season premiere was watched by 4.90 million viewers, higher than the entire second half of season two.