The Oscar-winning actor will be on hand to ring in the start to the Games, which will see wounded warriors compete in a series of sporting events in Orlando from May 8-12.
"The Invictus Games are a celebration of the human spirit and I am honored to be able to support these inspiring competitors who have embraced sport as part of their healing journey," Freeman said in a statement.
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"I hope that my fellow Americans will join me in Orlando to cheer on these magnificent men and women who are truly unconquerable, as the Invictus poem says, they are the masters of their fates, they are the captains of their souls."
Freeman, Hough and Johnson join Welsh singer Katherine Jenkins – another DWTS alum! – as supporters for the Paralympic competition featuring more than 500 competitors from 15 nations.
The five days of competition, which will unfold at ESPN Wide World of Sports Complex, includes everything from archery to wheelchair basketball to powerlifting and sitting volleyball.
Tickets for the Games can be bought here.