An 89th-minute header by Kai Havertz at the Gtech Community Stadium secured Arsenal a 1-0 win over Brentford as they moved to the summit of the Premier League.
After a slightly flat performance from Arsenal, Havertz entered the match as a late substitute and headed in a Bukayo Saka cross from close range.
At the other end, there had been pressure on Aaron Ramsdale, who was playing his first Premier League game for Arsenal since the start of September.
With David Raya unable to play against his parent club, Ramsdale survived a few nervy moments, and only a superb clearance off the line from Declan Rice prevented Aaron Wissa from scoring after Ramsdale gave the ball away close to his goal.
Arsenal had the better of the chances during the game and had a goal ruled out at the end of the first half after a VAR review found Leandro Trossard marginally offside when following up a saved header from Gabriel Jesus.
The Gunners leapfrog Manchester City and Liverpool into first place in the league after the two drew 1-1 in the lunchtime kick-off.