London - Alexis Sanchez's first Arsenal goal earned his side a nervy 1-0 victory over Besiktas on Wednesday that saw them squeeze into the Champions League for the 17th consecutive season.
The Chilean, Arsenal's number 17, repaid the first instalment of his £30 million transfer fee by tucking away a low shot in first-half stoppage time, but the hosts' inability to kill the game off made for a night of nail-biting tension at the Emirates Stadium.
Mathieu Debuchy's dismissal for two yellow cards meant that Arsenal saw out the last 15 minutes with 10 men, but although a solitary goal would have been enough to send the Turkish side through after last week's goalless draw in Istanbul, the hosts held on for a 1-0 aggregate win.
Arsene Wenger's side, who lost to Bayern Munich in the last 16 last season, will discover the identities of their group-phase opponents in Thursday's draw.
Arsenal were missing Aaron Ramsey through suspension, while Olivier Giroud's absence due to an ankle injury saw Sanchez handed another opportunity to prove he can lead the line on his own.
Though Arsenal initially took control, their chances owed more to serendipity than intricate build-up play.
Jack Wilshere slid a shot wide after Sanchez had been bundled over, while Santi Cazorla should have done better than slam the ball wide from 40 yards when visiting goalkeeper Tolga Zengin fluffed a kick.
Besiktas, meanwhile, had two penalty appeals waved away, first when Mustafa Pektemek tumbled under a challenge from Debuchy and then when Wilshere needlessly slid in from behind on Ramon Motta.
Reprieved, Wilshere then set Sanchez free, only for Zengin to save at the former Barcelona forward's feet, but in first-half injury time the same two players combined to put Arsenal ahead.
When Debuchy's cross was headed clear, Wilshere toed the ball to Mesut Ozil and although the England midfielder could not take the German's return pass into his stride, the ball broke kindly for Sanchez to roll a low shot past Zengin.
Eager to make their place in the group-phase safe, Arsenal started the second period strongly and forced the visitors onto the back foot.
Cazorla drilled the ball across goal from an Alex Oxlade-Chamberlain pass, Sanchez poked wide after being neatly teed up by Wilshere, and Debuchy headed wide at the back post from an in-swinging Cazorla free-kick.
The visitors remained a threat, however, and after Debuchy had alertly thwarted Demba Ba, the former Chelsea striker lashed a shot into the side-netting.
Oxlade-Chamberlain should have doubled Arsenal's lead when he shot straight at Zengin from Nacho Monreal's low cross and the hosts' task was further complicated when Debuchy saw red after tugging back Pektemek.
In a moment of farce, Wenger introduced defender Calum Chambers in place of Ozil, only for the former Southampton youngster to be booked by Portuguese official Pedro Proenca for entering the field of play too quickly.
With visiting coach Slaven Bilic watching animatedly from the stands following his dismissal in the first leg, Besiktas pressed hard in the closing stages, but Arsenal clung on to condemn their opponents to the Europa League.