President Barack Obama -- I Support Gay Marriage

For the first time in the history of the United States ... the sitting President has endorsed gay marriage.

In an interview with ABC News, President Barack Obama said, "I think same sex couples should be able to get married."

Obama explained, "I have to tell you that over the course of several years as I have talked to friends and family and neighbors when I think about members of my own staff who are in incredibly committed monogamous relationships, same-sex relationships, who are raising kids together, when I think about those soldiers or airmen or marines or sailors who are out there fighting on my behalf and yet feel constrained, even now that Don’t Ask Don’t Tell is gone, because they are not able to commit themselves in a marriage, at a certain point I’ve just concluded that for me personally it is important for me to go ahead and affirm that I think same sex couples should be able to get married."

The statement comes just days after Vice President Joe Biden threw his support behind gay marriage ... which seemingly forced the President to address the issue he had skirted throughout his presidency.

The whole issue's making serious waves across the Internet -- check out some celebrity responses.