The 25-year-old joined Albion from Celtic in August 2024, making 23 appearances in his first season with the club. On 2 September 2025, Ligue 1 side Marseille announced the season-long loan signing of O'Riley. He made his debut against Lorient in a 4-0 victory, coming off the bench. He scored his first goal against Metz.
Head coach Fabian Hurzeler says, “We’re pleased to welcome Matt back to the club. We know all about his qualities, and I have no doubt he will settle back into the group very quickly.
"He’s had a good spell with Marseille, playing regular domestic football and in the Champions League, and we believe he can positively impact the team in the second half of the season.”
Matt O’Riley made two Premier League appearances for Brighton at the start of this season, and scored from the penalty spot in the 1-1 draw with Fulham on the opening day.