Among other entertainment industry heavyweights, Anne Hathaway, Martin Sheen, Jane Lynch and Ellen DeGeneres signed an open letter sponsored by Freedom to Marry, a New York-based group promoting same-sex marriage rights.
Just weeks after President Obama's administration announced it would no longer legally defend the Defense of Marriage act, his supporters want him to go further.
"Whether to end discrimination in marriage is a question America has faced before. It is a question that calls for clarity from the president," the letter reads. "We ask you to join us, and the majority of Americans, who support the freedom to marry."
The letter was also signed by moguls David Geffen and Bob Wright; former NAACP chairman Julian Bond; and Facebook co-founders Chris Hughes and Sean Parker.
Hughes, who is gay, worked for Obama's campaign in 2008, heading its enormously successful social media efforts. But in 2011, the climate is a bit different.The president's relationship with Hollywood has noticeably cooled since 2008, as celebrities have openly expressed their discontent with Barack Obama.
Just last month, Matt Damon railed on Obama in an interview with CNN, bluntly saying he has not met expectations or done a good job as president.
Meanwhile, Lynch, the Emmy-winning, openly gay star of Glee, called him a "huge disappointment" for his handling of the gay rights issue specifically.
While generally regarded as well left of center, Obama has long said that he supports civil unions as an alternative to marriage for gays and lesbians.
That puts him to the right of former Vice President Dick Cheney, who has endorsed same-sex marriage. But in December, Obama admits his views on gay marriage are "evolving" and said he would continue "to wrestle" with the issue.