Art is no longer just a way to spend wealth—it's also become a creator of wealth.
A new study from Wealth-X, the Singapore-based wealth research firm, ranks the world's top billionaire art collectors by the value of their collections. The study found that the world's 2,170 billionaires hold an average of $31 million each of art, equal to 0.5 percent of their net worth.
The world's top, private art collection belongs to David Geffen, the music and entertainment mogul. Wealth-X said Geffen has $1.1 billion—or a fifth of his $5.5 billion fortune—in his art collection.
Geffen has been one of the smartest buyers and sellers in the art market for decades, having been an early collector of Jackson Pollock, Willem de Kooning and other postwar American artists. He reportedly sold a Pollock drip painting for $140 million in 2006 and a de Kooning for more than $130 million.
Ranking second is Steven Cohen, the founder of SAC Capital. Cohen's battles with government investigations and large investor withdrawals from his fund have not reduced his appetite for art.
(Read More: SAC: We Will Survive 'Significant' Redemptions)
Last fall, Cohen purchased Pablo Picasso's "La Reve" for $155 million. He also owns the famous pickled shark, the Damien Hirst creation of a shark floating in formaldehyde that is formally titled "The Physical Impossibility of Death in the Mind of Someone Living."
(See More: Picasso's La Reve: World's Best Investment)
Behind Cohen is Eli Broad, the real estate billionaire and major art backer, who has a wide-ranging collection including Jeff Koons, Andy Warhol and Andreas Gursky.
The billionaire with the highest concentration of his fortune in art is British-Iranian property tycoon Nasser David Khalili. Known as the "Secret Sultan," Khalili has almost all of his $1 billion fortune invested in his art collection, according to Wealth-X. He has a collection of more than 25,000 works, including the top collection of Islamic art and the top collection of Japanese kimonos.
(Read More: Top 1% Control 39% of World's Wealth)
Here are the other top billionaire art collectors along with the value of their collections:
1. David Geffen: $1.1 billion
2. Steven Cohen: $1 billion
2. Eli Broad: $1 billion
2. Boris Ivanishvili: $1 billion
2. Francois Pinault: $1 billion
3. Nasser David Khalili: $930 million
4. Norman Braman: $900 million
5. Doris Fisher: $800 million
6. Leon Black: $750 million
7: S.I. Newhouse Jr.: $700 million
—By CNBC's Robert Frank. Follow him on Twitter