Hollywood actor Brad Pitt has donated $100,000 to fight Proposition 8, the California constitutional amendment that would ban gay marriage, reports The Associated Press.

Pitt, a long-time gay ally, made his donation to the No on Prop 8 campaign – the single largest so far by a celebrity.

“Because no one has the right to deny another their life even though they disagree with it, because everyone has the right to live the life they so desire if it doesn't harm another, and because discrimination has no place in America, my vote will be for equality and against Proposition 8,” Pitt said in a statement.

The California Supreme Court overruled a 2000 voter-approved gay marriage ban in May. Since then thousands of gay and lesbian couples have married in the State. But a November ballot initiative seeks to reverse the pro-gay marriage ruling by amending the State's constitution.

Several high-profile gay and lesbian celebrity couples have tied the knot in the Golden State. Talk show host Ellen Degeneres married her girlfriend Portia de Rossi last month, and George Takei (Star Trek, Heroes) and Brad Altman married in Los Angeles over the weekend.

Donations are needed because groups opposing gay marriage continue to pour money into California. Californians Against Hate, a group dedicated to exposing the anti-gay money trail, says gay marriage opponents are raking in nearly $10 million a month.