Now you can own it. The singer/songwriter/producer is auctioning off the topper to raise money for charity.
Williams, 40, has put the Vivienne Westwood "Mountain" hat up for auction on eBay. Proceeds from the sale will benefit One Hand to Another, an organization he founded that helps underserved youth.
"Now is your chance to own a piece of pop culture history!" the listing description says. "Bid on Pharrell Williams' Vivienne Westwood 'Mountain' hat that was one of the biggest hits of the 2014 Grammy Awards."
He posted a link to the auction on Twitter, showing himself wearing the hat. "Hey @Arbys, you want my hat? Now's your chance…" he wrote, referencing a tweet the fast-food chain sent about the hat on Grammys night.
The auction continues through March 2, but you'll need deep pockets if you want to join in -- bidding has already reached $10,500.
Williams -- with or without a new hat -- is also set to perform at the Oscars on March 2, where his song "Happy" from "Despicable Me 2" is nominated for best original song.