London Welsh staged a remarkable late comeback to defeat Bath and boost their hopes of Premiership survival.
Bath led 9-6 with two minutes remaining, but a Gordon Ross penalty levelled the scores.
And winger Nick Scott raced in from 70 yards in the final seconds to earn the Exiles their third league win.
Earlier, Gavin Henson and Stephen Donald had exchanged first-half penalties before an enthralling finish at the Kassam Stadium.
London Welsh remain 10th in the table but are now eight points clear of bottom club Sale Sharks, who picked up their first win of the campaign against second-bottom London Irish on Friday.
Before Scott's score, which came after he intercepted Donald's misplaced pass, the home side had rarely threatened the try line, while visitors Bath were unable to convert any of the chances they created.
Bath trailed 6-3 at half-time, with Henson slotting over two penalties to Donald's one, but the New Zealand international restored parity and then kicked his side ahead with a brace of penalties early in the second half.
It looked like being enough for victory, until Scott's late heroics sealed a first win for the Exiles over Bath since 1979.
VIEW FROM THE DRESSING ROOM
London Welsh head coach Lyn Jones:
"I can't quite believe it. We snatched victory from the jaws of defeat.
"We've had a few hard lines in the last few weeks - a tough last-minute call against Saracens and we carelessly lost a bonus point last week against Wasps.
"We stuck in there and kept battling. Our effort was very good and our first-half performance was our best of the season.
"It's pleasing that we kept our line in tact as we conceded five tries against Leicester and six against Harlequins, but the penalties we gave away show that we are still a little bit immature."
Bath director of rugby Gary Gold:
"I'm astonished [with Donald's pass]. It was a rush of blood and a ridiculous pass.
"We had worked so hard to get into that position, as for 79 minutes we had been effective at holding onto the ball.
"We should have retained possession and, if needs be, go back into the pocket and drop a goal."
London Welsh: Arscott; Voyce, Tonga'uiha, Jewell, Scott; Henson, Keats; Montanella, Briggs, Ion; Purdy, Kulemin; Mills, Denbee, Beach.
Replacements: Ross for Henson (58), Bateman for Montanella (65), Jolly for Ion (64), Brown for Kulemin (77), Bristow for Denbee (77), Browne for Beach (58).
Not Used: Runciman, Lewis.
Bath: Abendanon; Eastmond, Banahan, Williams, Biggs; Donald, Claassens; James, Mears, Perenise; Day, Attwood; Hooper, Mercer, Skuse.
Replacements: Agulla for Banahan (58), Taylor for Day (57).
Not Used: Sharman, Beech, Palma-Newport, Ovens, McMillan, Vesty.
Referee: Andrew Small (RFU)