Strachan has been linked with the vacancy at Sunderland
Gordon Strachan is leaving Celtic just one day after surrendering the Scottish Premier League title to Rangers.
Strachan began his four-year tenure with three consecutive league successes but his side let slip a seven-point lead established by the end of 2008.
The 52-year-old former Southampton boss is now thought to be among those being considered for the Sunderland vacancy.
"It has been an absolute honour and privilege to be the club's manager for four years," said Strachan.
"We have done all we can to bring success to the club and we were delighted to deliver three SPL titles, other domestic silverware, as well as making some great progress in Europe.
"It is just disappointing that we did not manage the fourth championship. However, the players can hold their heads high in terms of what they have done in recent years.
"I would like to thank the Celtic board for all the support they have given me, in particular Dermot Desmond, John Reid, Peter Lawwell and former chairman Brian Quinn - I could not have asked for any more support.
"I thank all the players I have worked with at the club and, of course, my backroom team for the backing and assistance which they have given me.
"I thank the fans too for the tremendous support which they have given both myself and the players. I wish Celtic and our supporters nothing but success for the future."
A return to English football could now beckon, with Strachan thought to be interested in the Sunderland vacancy.
Strachan, who won 50 caps for Scotland, began his career with Dundee, before moving on to Aberdeen, Manchester United, Leeds United and finally Coventry City.
Following a break of more than a year after standing down at Southampton, he returned to management to succeed Martin O'Neill at Celtic Park on 1 June 2005 and had an embarrassing start to his reign, losing 5-0 to Slovakian champions Artmedia Bratislava in a Champions League qualifier.
Gordon Strachan's career at Celtic
Three days later, Celtic only managed to draw 4-4 with Motherwell in his first match in the SPL.
After that wobble and, although they led the SPL by 20 points, Strachan again suffered criticism when Celtic were knocked out of the Scottish Cup by First Division Clyde.
That first season ended with a League Cup and league double and a manager of the year award from the Scottish Football Writers' Association.
By January of the next season, Celtic held a 17-point lead in the SPL standings and progressed to the final 16 of the Champions League for the first time, losing to eventual winners AC Milan in extra time.
A 41st league championship was secured and Celtic went on to beat Dunfermline in the Scottish Cup final.
Strachan again led the Glasgow outfit into the last 16 of the Champions League and, last season, became only the third-ever Celtic manager to lead the club to three consecutive Scottish league titles.
Strachan won three league titles in his four years with Celtic
Despite his excellent record, Strachan struggled to completely win over the club's supporters, in contrast to the widespread adulation enjoyed by his predecessor O'Neill.
This season brought another League Cup victory but there was criticism of Celtic's playing style and Strachan's team selections, although he could argue an injection of quality to his squad in January, when they had the edge over Rangers, may have made the difference.
Only Willo Flood from Dundee United was added to the first team squad and he barely featured in the run-in.
A high-profile dressing-room bust-up with Aiden McGeady, which led to a two-week suspension and club fine for the Republic of Ireland star, was a test of character for Strachan.
And his decision to omit McGeady from the starting line-up in the recent 1-0 loss to Rangers at Ibrox also attracted flak from fans.
Celtic needed a win at Hibernian on the penultimate game of the league campaign to go level on points with Rangers, with a better goal difference, but were held to a 0-0 draw.
And the season fizzled out with another blank scoreline at home to Hearts, as Rangers secured the title with a win over Dundee United at Tannadice.
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