Celtic completed an aggregate victory against HJK Helsinki to progress to the Champions League play-off round.
Scott Brown threatened as the visitors sought to cancel out HJK's away goal and the hosts' Sebastian Sorsa and Mathias Lindstrom had efforts saved.
Ledley chested the ball past Ville Wallen to give Celtic the lead on the night in the 68th minute.
A second booking meant a dismissal for Victor Wanyama but the 10 men added to their lead with Georgios Samaras' shot.
Neil Lennon's side will discover who they will face in the next round when the draw is made on Friday.
Celtic captain Brown, a pre-match fitness doubt, beat the offside trap to latch on to Charlie Mulgrew's terrific lofted pass but goalkeeper Wallen was untested as the midfielder placed his shot wide.
The artificial surface seemed to be posing no problems for the Scottish champions and Samaras chested down another high ball before flashing a dipping volley past Wallen's left-hand post.
The Finns were struggling to carve out chances and Demba Savage failed to connect with Sorsa's cross in their best first-half attack.
But HJK pressed hard at the beginning of the second period and Sorsa's low drive from the edge of the box was turned out by Forster.
Kris Commons' curling free-kick was met by Wanyama and Celtic's claims of handball after the header had been blocked were turned down by Austrian referee Robert Schorgenhofer.
Lindstrom was unchallenged at Rasmus Schuller's corner and the defender nodded the ball into the ground only for Forster to awkwardly usher it out on the bounce.
The breakthrough arrived when Mulgrew found himself forward on the right in a Celtic break and his inswinging cross was forced past Wallen by the chest of Ledley.
But Celtic soon found themselves down to 10 men as Wanyama's foul on Mika Vayrynen resulted in a second yellow card and a suspension for the Kenyan.
It did not upset Celtic's rhythm though and Ledley's perseverance on the left was rewarded when Samaras collected the Welshman's cutback and placed a low shot into the net to confirm the Glasgow side's first away European win in three years.
Progress ensures Celtic will play group stage football this season with a parachute into the Europa League available if they lose their Champions League play-off.
- 01 Wallen
- 06 Lahti
- 11 Lindstrom
- 07 Mannstrom (Zeneli - 74' )
- 16 Vayrynen
- 21 Sumusalo
- 22 Perovuo (Sadik - 69' )
- 26 Savage Booked
- 27 Sorsa
- 28 Schuller
- 20 Pohjanpalo (Pelvas - 78' )
- 35 Sahlgren
- 02 Kansikas
- 04 Okkonen
- 05 Hakanpaa
- 08 Zeneli
- 09 Sadik
- 15 Pelvas
- 01 Forster
- 02 Matthews
- 03 Izaguirre
- 21 Mulgrew Booked
- 25 Rogne
- 08 Brown Booked
- 15 Commons Booked (Forrest - 74' )
- 16 Ledley
- 67 Wanyama Dismissed after an earlier booking
- 09 Samaras (Murphy - 88' )
- 88 Hooper (Kayal - 74' Booked )
- 24 Zaluska
- 23 Lustig
- 20 McCourt
- 33 Kayal
- 49 Forrest
- 10 Stokes
- 27 Murphy
Live Text Commentary
Full Time The referee blows his whistle to end the game.90:00 +1:08
Mika Vayrynen concedes a free kick for a foul on Charlie Mulgrew. Charlie Mulgrew restarts play with the free kick.88:14
Free kick taken by Fraser Forster.88:14 Booking
Booking Demba Savage receives a yellow card for unsporting behaviour.88:01
The official flags Demba Savage offside.86:58
Mikko Sumusalo takes the direct free kick.86:58 Substitution
Substitution Daryl Murphy is brought on as a substitute for Georgios Samaras.86:58 Booking
Booking Caution for Scott Brown.86:47
Scott Brown concedes a free kick for a foul on Demba Savage.85:33
Assist on the goal came from Joe Ledley.85:33 Goal scored
Goal! - Georgios Samaras - H Helsinki 0 - 2 Celtic Georgios Samaras gets on the score sheet with a goal from inside the box to the bottom right corner of the goal. HJK Helsinki 0 (1)-(4) 2 Celtic.84:12
Erfan Zeneli has an effort direct from the free kick.84:12 Booking
Booking Booking for Beram Kayal for unsporting behaviour.84:08
Beram Kayal challenges Demba Savage unfairly and gives away a free kick.81:47
Mika Vayrynen has an effort at goal from outside the penalty box missing to the wide left of the goal.79:13
The referee blows for offside. Fraser Forster takes the indirect free kick.78:58
Unfair challenge on Mathias Lindstrom by Georgios Samaras results in a free kick. Free kick taken by Mika Vayrynen.77:43 Substitution
Substitution Akseli Pelvas comes on in place of Joel Pohjanpalo.73:31 Substitution
Substitution Kris Commons goes off and James Forrest comes on.73:31 Substitution
Substitution Beram Kayal joins the action as a substitute, replacing Gary Hooper.
Substitution Erfan Zeneli replaces Sebastian Mannstrom.71:23
Mikko Sumusalo takes the direct free kick.70:56 Dismissal
Dismissal Victor Wanyama is shown a red card.70:41
Victor Wanyama challenges Mika Vayrynen unfairly and gives away a free kick.68:47
Mikko Sumusalo crosses the ball from the free kick left-footed from right channel, comfortable save by Fraser Forster.68:47 Substitution
Substitution Joel Perovuo goes off and Berat Sadik comes on.68:47
Free kick awarded for an unfair challenge on Sebastian Sorsa by Emilio Izaguirre.66:25
Assist by Charlie Mulgrew.66:25 Goal scored
Goal! - Joe Ledley - H Helsinki 0 - 1 Celtic Joe Ledley grabs a headed goal from close in. HJK Helsinki 0 (1)-(3) 1 Celtic.66:18
The ball is delivered by Charlie Mulgrew,63:52
Unfair challenge on Joe Ledley by Sebastian Sorsa results in a free kick. Kris Commons crosses the ball from the free kick left-footed from left wing.62:32
Corner taken left-footed by Kris Commons, save made by Ville Wallen.61:55
Inswinging corner taken by Rasmus Schuller, save made by Fraser Forster.61:18
Sebastian Mannstrom takes the inswinging corner, Mathias Lindstrom takes a shot. Save by Fraser Forster.59:39
Free kick awarded for an unfair challenge on Timi Lahti by Gary Hooper. Direct free kick taken by Joel Perovuo.58:37
The ball is crossed by Adam Matthews.56:18
Sebastian Mannstrom challenges Georgios Samaras unfairly and gives away a free kick. Charlie Mulgrew takes the direct free kick.54:33
Corner taken right-footed by Sebastian Mannstrom, clearance by Kris Commons.53:51
Rasmus Schuller delivers the ball from the free kick left-footed from right by-line, Thomas Rogne manages to make a clearance.53:51 Booking
Booking Victor Wanyama shown a yellow card.53:44
Free kick awarded for a foul by Victor Wanyama on Sebastian Sorsa.52:13
Free kick taken by Mika Vayrynen.52:13 Booking
Booking Charlie Mulgrew shown a yellow card.51:57
Free kick awarded for a foul by Charlie Mulgrew on Joel Perovuo.51:20
Foul by Mika Vayrynen on Charlie Mulgrew, free kick awarded. Free kick crossed left-footed by Kris Commons from left wing.50:12
Demba Savage is flagged offside by the assistant referee. Fraser Forster takes the indirect free kick.46:49
Corner taken right-footed by Sebastian Mannstrom from the left by-line, clearance by Thomas Rogne.46:32
Drilled right-footed shot by Sebastian Sorsa. Fantastic save by Fraser Forster.45:01
The second half kicks off.45:00 +1:04 Half time
Half Time The referee calls an end to the first half.43:19
Foul by Mikko Sumusalo on Kris Commons, free kick awarded. Free kick taken by Charlie Mulgrew.41:49
Unfair challenge on Mathias Lindstrom by Georgios Samaras results in a free kick. Ville Wallen restarts play with the free kick.39:20
Unfair challenge on Sebastian Mannstrom by Emilio Izaguirre results in a free kick. Free kick taken by Mika Vayrynen.38:53
Shot by Mika Vayrynen from 20 yards. Save by Fraser Forster.36:49
Foul by Joe Ledley on Sebastian Mannstrom, free kick awarded. Direct free kick taken by Mathias Lindstrom.35:09
The ball is swung over by Sebastian Sorsa.32:27
Free kick awarded for a foul by Georgios Samaras on Sebastian Sorsa. Sebastian Sorsa takes the free kick.31:18
Foul by Sebastian Mannstrom on Charlie Mulgrew, free kick awarded. Direct free kick taken by Fraser Forster.28:47
Gary Hooper is caught offside. Ville Wallen takes the free kick.27:47
Georgios Samaras concedes a free kick for a foul on Sebastian Sorsa. Sebastian Sorsa takes the direct free kick.26:37
Timi Lahti takes the free kick.26:37 Booking
Booking Kris Commons booked.26:25
Foul by Gary Hooper on Timi Lahti, free kick awarded.24:50
Sebastian Mannstrom fouled by Scott Brown, the ref awards a free kick. Ville Wallen takes the free kick.24:20
Inswinging corner taken by Kris Commons from the right by-line, save by Ville Wallen.23:46
Sebastian Sorsa concedes a free kick for a foul on Georgios Samaras. Charlie Mulgrew restarts play with the free kick.22:45
Corner taken by Sebastian Mannstrom, clearance made by Georgios Samaras.22:13
Gary Hooper challenges Timi Lahti unfairly and gives away a free kick. Timi Lahti restarts play with the free kick.21:05
Unfair challenge on Demba Savage by Scott Brown results in a free kick. Mika Vayrynen takes the free kick.20:51
Emilio Izaguirre concedes a free kick for a foul on Joel Perovuo. Timi Lahti takes the free kick.13:52
Effort from the edge of the area by Georgios Samaras goes wide of the right-hand upright.12:21
Effort on goal by Scott Brown from deep inside the penalty area misses to the right of the goal.8:56
Kris Commons has an effort at goal from 18 yards. Save by Ville Wallen.6:59
Demba Savage produces a right-footed shot from just outside the area that goes harmlessly over the bar.2:27
Scott Brown is penalised for handball and concedes a free kick. Timi Lahti restarts play with the free kick.0:32
Free kick awarded for a foul by Emilio Izaguirre on Sebastian Sorsa. The free kick is swung in left-footed by Rasmus Schuller, Victor Wanyama manages to make a clearance.0:00
The match begins.
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