NEOM McLaren had signed Rast at the close of Season 8, with the German the first of the team's driver line-up to be announced ahead of its Formula E bow in Season 9.
The team said in a statement: "Rene has been an integral part of the team’s successes and learnings as its first season as the NEOM McLaren Formula E Team. Rene has taken the difficult decision to pursue other opportunities, and the team fully supports his decision. We can’t thank him enough for everything he’s done for the team over the past year.
"Having said that, the team has been working in the background to secure the best possible driver line-up for Season 10, and we are excited to announce the full driver line-up for the 2023/24 season of the ABB FIA Formula E World Championship in due course.
"Thank you again, Rene – you will be missed."
Rast made his return to Formula E after a full-time spell with Audi Sport ABT Schaeffler back in Season 7, with a best result of second in Puebla. The Minden-born driver's first appearance in the series came back in 2015/16 and was followed by a stint with Audi back at the Season 6 six-race nine-day finale in Berlin that earned him a full-time drive a year later. He scored his first Formula E silverware on home soil in the German capital, having impressed with his swashbuckling, combative driving style.
The triple DTM champion went on to score McLaren's only podium of the season, in Diriyah, and finished just eight points behind rookie Jake Hughes in the sister car - winding up 13th in the Drivers' World Championship. A tough run through the second half of the season from his home E-Prix in Berlin onwards saw him fail to finish higher than 12th.