Bristol's Shaun Perry was forced off injured in the second half
Bristol: (8) 16
Tries: Llewellyn, Robinson
Pens: Hill 2
Bath (6) 6
Pens: Barkley 2
Bristol won the West country derby in front of a Premiership record crowd for a club venue of 21,203 at Bristol City's Ashton Gate ground.
Bristol led 8-6 at the break courtesy of a Gareth Llewellyn try and Dave Hill penalty to two Olly Barkley penalties.
With Bath temporarily down to 14 men Hill then landed his second penalty to edge Bristol five points clear.
And the hosts ensured they went back to the top of the table when Lee Robinson plundered Bristol's second try late on.
Bristol had moved the match from their Memorial Ground across the city to Ashton Gate and the attendance was the biggest ever at a regular season Premiership game outside of the season-opening Twickenham double header.
However, the hosts' lack of familiarity with their surroundings was all too apparent as they started like the visiting team, with Bath dominating the opening stages.
Barkley slotted a 10th minute penalty to edge them into the lead and it took a couple of meaty scrums from the vastly experienced Bristol pack to settle the hosts down.
They came desperately close to scoring through Samoan winger David Lemi and finally gave their fans in the huge crowd something to cheer about in the 32nd minute.
After kicking a penalty into the corner the 37-year-old second-row Llewellyn stretched over from the line-out. Hill missed the conversion.
Given his advanced years you would have thought Llewellyn would have learned not to punch people in front of the referee, but shortly after his try he could not resist the temptation to hit Danny Grewcock.
Barkley stepped up to nudge Bath back in front from the resultant penalty but Hill soon replied in kind after a powerful burst from Bristol number eight Dan Ward-Smith.
Bath's Peter Short was sin-binned after he got in the way of what could have been a try-scoring pass and Bristol led 8-6 at half-time.
A second Hill penalty soon after the re-start edged the hosts into a five-point lead and as the match entered the final quarter both teams found themselves reduced to 14 men as hookers Mark Reagan and Lee Mears were yellow carded.
Chances were at a premium and it took a fine kick from Hill to enable Bristol to make the game safe.
The fly-half's kick to the corner was inch-perfect, Robinson climbed miles into the night sky to claim the ball and the powerful winger just managed to get it down before being bundled out of the dead-ball area.
Hill missed the conversion and a late penalty but victory, and West country bragging rights, were secure.
Bristol boss Richard Hill:
"It is a tremendous win and scoring two tries was important having conceded six at Leicester.
"We didn't get much ball in the first half. They had so much possession and line breaks that we could have been three scores down by the interval.
"No motivation was required in the dressing room at half-time but we had to settle down and play more relaxed."
Bath head coach Steve Meehan:
"If our set piece had performed better in the second half then we could have put Bristol under some pressure and perhaps we could have won the match.
"The defeat is disappointing for the players coming after the Sale victory.
"We felt that we showed that we were maturing as a side but in this game we couldn't capitalise on anything that we created."
Bristol: Morgan; Robinson, Cox, Taumalolo, Lemi; Hill, Perry; Clarke, Regan, Crompton, Winters, Llewellyn, To'oala, El Abd, Ward-Smith. Replacements: Nelson, Hilton, Budgett, Salter, O'Riordan, Strange, Lima.
Bath: Stephenson; Maddock, Fuimaono-Sapolu, Barkley, Bory; Berne, Walshe; Barnes, Mears, Ovens, Short, Grewcock, Beattie, Scaysbrook, Feau'nati. Replacements: Dixon, Sigley, Fidler, Faamatuainu, Louw, Williams, Walker.
Referee: Sean Davey (RFU)