Carabao Cup: Porter, 16, becomes Arsenal's youngest player to start.
Mikel Arteta has selected the 16-year-old for Tuesday's Carabao Cup match against Bolton Wanderers.
The teenager only signed scholarship terms with the Premier League this summer, having turned 16 in July.
Porter has made only a few appearances for Arsenal's Under-23s, let alone the big squad.
However, with David Raya injured at Manchester City on Sunday and Neto cup-tied, the youth is given his opportunity.
Ethan Nwaneri, 17, made history as Arsenal's youngest Premier League player when he faced Brentford in September 2022.
Last season, the midfielder appeared for 15 minutes as a substitute in Arsenal's 6-0 victory over West Ham.