Reynolds has recently emerged as a prominent figure in Welsh football after buying a controlling share in Wrexham AFC, in partnership with It’s Always Sunny in Philadelphia star Rob McElhenney.
Wales have not participated in a World Cup tournament since 1958, when they reached the quarter-finals.
Reynolds expressed his support for the side in a video recorded for WalesOnline.
“Hey, this is Ryan Reynolds,” he says in the clip. “I just wanted to send all my best wishes to the entire Welsh football club on their way to Qatar to compete at the World Cup.
“I’m actually sitting here right now with my best friend and my co-pilot at Wrexham AFC, Mr Rob McElhenney.”
McElhenney, however, stopped short of backing the Welsh contingent against his native USA.
“I just want to say ‘good luck but not too much luck’,” McElhenney quipped. “I mean, maybe a draw. A draw would be nice. Play your hearts out, though.”
“I’m so sorry about him,” Reynolds replied. “Crush all of your enemies; drink the blood of your enemies.
“Rob and I are actually in the car right now because we are driving to Qatar. Go get ’em.”
Wales’s first match, against the US, takes place at 7pm GMT on Monday 21 November.
Players including former Real Madrid winger Gareth Bale and ex-Arsenal midfielder Aaron Ramsey are expected to feature for Wales, while Christian Pulisic and Gio Reyna will likely star for the US.