Report: Lance Armstrong CONFESSES to Oprah -- YES, I CHEATED

Lance Armstrong ADMITTED to Oprah Winfrey ... he DID use performance-enhancing drugs during his pro cycling career to win the Tour de France ... this according to the Associated Press.

Lance wrapped up his one-on-one interview with Oprah just a few hours ago ... and according to the report, Lance finally 'fessed up to cheating ... the first time he's ever admitted wrongdoing during his professional career.

Earlier in the day, Lance apologized to the staff at Livestrong, choking up and saying he was sorry for letting down the organization.

The way Lance worded his admission could have serious legal ramifications -- considering he's facing possible criminal prosecution and civil liability for allegedly lying about his PED use in a number of legal proceedings.