Plymouth Albion produced a stirring display at Brickfields to end Championship leaders Exeter Chiefs' unbeaten league record.
Albion took the lead after 15 minutes when they were awarded a penalty try after Chiefs collapsed a rolling maul.
An exchange of penalties took the score up to 10-6 at half-time.
Two penalties from Alex Davies extended Albion's lead after the break, and then Keni Fisilau touched down to put the home side clear.
The Chiefs did manage to score a late try through winger Mark Foster.
But Plymouth held on to claim their first win over their local rivals since 2005.
Despite the defeat, Exeter remain on top of the Championship table, although their lead over Bristol has now been cut to a single point ahead of their meeting on 27 December.
Albion are now up to seventh in the league table.