Denise Rich threw a lavish carnival-themed party in St. Tropez harbor last night. The songwriter, whose fugitive ex-husband, Marc Rich, died last month, threw the rager on her yacht the Lady Joy, with guests including casino mogul Steve Wynn, Joan Collins, Ivana Trump (who’s back with her much younger ex-husband Rossano Rubicondi), Star Jones, Dori Cooperman, Magic Johnson and Blackstone’s Steve Schwarzman. Denise recently dumped her US citizenship for tax reasons. A spy told us, “The entire dock is covered in red carpet. Huge stars are hanging like balloons. Women are doing circus acts above the dance floor, which is rotating in a circle with a big top over it. Oh, yes.”