Arsenal had led through a bizarre early Cesc Fabregas goal, had Alex Song sent off after 55 minutes and saw Tomas Rosicky blaze a 74th minute penalty over the bar but just when it seemed they had held out for the win England striker Bent struck.
Earlier some inspired substitutions gave a relieved Tottenham Hotspur a 3-1 home win over Wolverhampton Wanderers as Harry Redknapp's team scored three in the last 13 minutes to move up to fourth spot with eight points from five games.
Everton could not repeat their own comeback heroics from last week as they lost at home in the league for the first time in 10 months via a superb 45th-minute strike by Newcastle United's Hatem Ben Arfa to leave them second-last on two points.
Birmingham City's unbeaten start to the season ended as West Bromwich Albion came from 1-0 down at half-time with three goals in 10 minutes to win 3-1.
Aston Villa against Bolton Wanderers, Blackburn Rovers v Fulham and Stoke City against West Ham United all ended 1-1.
EXTRAORDINARY MATCH
Second-placed Arsenal were within seconds of displacing their London rivals at the top of the standings following an extraordinary encounter in the north-east.
After manager Arsene Wenger raised hackles all round the league this week by complaining about other teams' over-physical approach it was his side who were the aggressors against a Sunderland outfit playing most of the football.
If their approach was unusual, so was their goal, as Fabregas blocked an Anton Ferdinand clearance then watched in amazement as the ball flew 35 metres into the net over the head of bemused Sunderland goalkeeper Simon Mignolet.
The Spain midfielder sustained a hamstring strain in the incident and went off after 30 minutes.
Arsenal, who scored 18 goals in their previous four games, defended doggedly in the face of relentless Sunderland pressure, particularly after Song's dismissal for a second booking.
Even when Rosicky blasted a fortunate penalty over the bar after a foul on Samir Nasri it seemed they would get away with it but Sunderland threw everyone forward and Bent banged in a deserved equaliser, sending the home fans almost as wild as Wenger.
"I know it's a minimum of four minutes but nothing happened in those four minutes to justify them adding more," the furious Frenchman told ESPN.
"I believe the performance was good. We had problems starting in the first half, in the second half we played very well with 10 men and were in control of the game. Unfortunately, in the 95th minute they equalised," he added.
Sunderland manager Steve Bruce said: "They got a fluke of a goal. We got our reward for a very good performance."
SMART SUBSTITUTIONS
