Montgomerie, who won Europe's money title seven straight times, issued a brief statement Thursday with wife, Eimear.
'We have sadly decided to separate, with a view to divorce,' the statement said. 'This has been a desperately difficult decision for us both and is a painful time for the family.'
Montgomerie and his wife separated several years ago, a split he blamed on his heavy golf schedule, but reconciled. The couple have three children.
Montgomerie withdrew from this week's China Masters in Beijing, citing 'personal reasons.'
There are also doubts about his participation in this summer's British Open, which will be played at his home course - Royal Troon near Ayr, Scotland.
Montgomerie was Europe's No. 1 player in the late '90s and reached the world No. 2 ranking in that period.
News reports have suggested his wife has grown close to British actor Hugh Grant, a relationship she and the actor have denied.
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