The Scotland international, who joined the Dragons from Wigan in 2017, scored 22 tries in 66 games for the French side.
A Catalans statement said: “We would like to wish him all the best for the future. Thanks Lewis!”
Leigh head coach John Duffy expects the 26-year-old to fit straight in.
“Lewis is an outstanding signing for us, first of all he is an outstanding person and someone who I have known all of his life,” Duffy said.
“He has come through the pathway at Wigan winning major trophies and kicked on to be remembered at Catalans for their Challenge Cup Final win not too long ago.
“He will fit straight into our growing squad and will flourish with the way we want to play. I can’t wait to see him and get going.”
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