David Gilmour isn’t satisfied being “Comfortably Numb” when it comes to the planet.

The Pink Floyd axeman auctioned his guitars for $21 million Thursday — and he’s donating every penny to ClientEarth, a nonprofit fighting climate change.

“The global climate crisis is the greatest challenge that humanity will ever face, and we are within a few years of the effects of global warming being irreversible,” tweeted Gilmour, the singer, guitarist and songwriter for the legendary Brit rock band.

“We need a civilized world that goes on for all our grandchildren and beyond in which these guitars can be played and songs can be sung.”

Christie’s, which handled the sale, said this is the largest and most comprehensive sale of guitars ever offered at auction.

But the star attraction was Gilmour’s legendary Black Strat — it was snatched off the block by Indianapolis Colts owner Jim Irsay for $3,975,000 — setting a new world record for any guitar sold at auction, Christie’s said.

The is the axe heard on Pink Floyd’s “Comfortably Numb,” “Shine on You Crazy Diamond,” “Money” and many others, Guitar World’s Jackson Maxwell reported.

“The guitar went through many modifications over the years, which only added to its mystique,” Maxwell said. “With its battle-scarred surface, it wouldn’t be hard to believe this guitar had been to The Dark Side of the Moon and back. And in some ways, it had, appearing on that album, as well as many others in the Floyd catalog.”

Parting with his guitar collection is something Gilmour has pondered for years.

“These guitars have served me very well. They’ve given me songs and tunes, but I thought it would be good for them to move on and create new music with different people,” he told Guitar World. ” Hopefully, they’ll also raise a fair bit of money, which I plan donate to charity, and that will do some direct good in this world with all its difficulties.”

ClientEarth is a “charity that uses the power of the law to protect the planet and the people who live on it,” according to its website.

“This is a truly humbling and extraordinary gift, which goes beyond our wildest expectations,” ClientEarth CEO James Thornton said in a statement. “It’s difficult to express just how deeply grateful we are to David for choosing ClientEarth as the beneficiary of this historic auction.”