Heinz-Harald Frentzen will drive for Arrows in this season's Formula One World Championship.
The German (34), who left Jordan after last year's British Grand Prix and joined Prost, was looking for a new outfit after the collapse of the French team because of financial problems.
Frentzen, who will be Arrows' number one with Enrique Bernoldi the team's other driver, said: "I'm very much looking forward to racing for OrangeArrows.
"The team has a fantastic facility and a lot of very talented and dedicated people. All the ingredients are there to take a major step forward and I'm convinced we will be successful."
"We're very pleased that Heinz-Harald is joining the team," OrangeArrows team principal Tom Walkinshaw said in a statement. "He is a recognised top-line driver and has proved his mettle by winning three Grands Prix during his career".
Frentzen will drive the A23 for the first time today in Valencia, where Arrows have begun testing.
