Bill Gates & Warren Buffett -- Mercilessly Paddled

56-year-old Bill Gates and 81-year-old Warren Buffett lost control of their balls yesterday -- getting their asses WHOOPED by a teenage ping pong prodigy in Nebraska ... and the footage is hilarious.

Bill and Warren were in town for some business conference thing in Omaha -- where they faced off against 16-year-old Ariel Hsing ... a current member of the U.S. Olympic table tennis team.

Needless to say, they didn't last very long -- until Buffett whipped out his over-sized secret weapon.

FYI -- it's the second time Ariel has kicked Buffett's ass ... the two previously went head-to-head in 2007 when Ariel was just 11 years old (below).