Daniel Theis (/taɪs/;[1] born 4 April 1992) is a German professional basketball player for the AS Monaco of the French LNB Élite and the EuroLeague.

[11] On 29 October 2018, Theis was found to have a slight tear of the plantar fascia in his right foot and was scheduled to be out indefinitely, but he returned shortly after the injury on 11 November vs. the Portland Trail Blazers.

[16] Celtics coach Brad Stevens said that Theis complemented the rest of the starters, playing in a way that "fits the other guys perfect.

[21] On 10 February 2022, the Boston Celtics re-acquired Theis from the Rockets in exchange for Bruno Fernando, Enes Freedom, and Dennis Schröder.

On 9 July 2022, Theis was traded, alongside Nik Stauskas, Aaron Nesmith, Malik Fitts, Juwan Morgan and a 2023 first-round pick, to the Indiana Pacers in exchange for Malcolm Brogdon.

[23] On 2 February 2023, after missing over 50 games due to knee surgery, Theis made his Pacers debut against the Los Angeles Lakers.

[25] Theis spent his first season in Indiana as a mentor and backup to Myles Turner, Jalen Smith, and Isaiah Jackson before falling out of the Pacers rotation.

[29] On 5 February 2025, Theis was traded alongside a 2031 second-round pick to the Oklahoma City Thunder in exchange for cash considerations.

[37] Heading toward EuroBasket 2022, Theis helped Germany win bronze during the tournament, finishing with 8.8 points, 6.1 rebounds and 1.3 assists per game.