TMZ has learned the secret identities of THREE new celebrity contestants on the upcoming season of "Dancing with the Stars" -- most interesting ... Heather Locklear's ex and "Melrose Place" actor Jack Wagner. You'll recall Jack and Heather got into an epic fight in December that triggered a 911 call.
Sources connected with the production tell TMZ, Sherri Shepherd from "The View" will also be competing in the upcoming season ... which kicks off next month.
As for the third -- that would be "Little House on the Prairie" star Melissa Gilbert, who was rumored to be on last season ... but that deal fell through.
We shot Melissa on her way into practice today at an L.A. dance studio (below) -- she was pretty tight-lipped.