Rory McIlroy played last week's Open Championship having broken up with girlfriend Holly Sweeney.
The US Open champion's management company issued a statement on Monday night saying: "Rory McIlroy's long-time relationship with Holly Sweeney came to an amicable end before the Open Championship."
The pair had a period apart earlier in the year, but 20-year-old student Sweeney, a cheerleader for the Ulster rugby team, was at Augusta to greet him after his hopes of winning The Masters were crushed by a closing 80.
She did not attend last month's US Open, where he claimed his first major title by an incredible eight shots and with a record score, but wrote on Twitter: "My fabulous boyfriend has played flawlessly all week!
"Drink up Northern Ireland, he's done us proud! Champagne flowing .?.?. Sooo happy for the curly one! 1st major down, millions to go!"
On Sunday night BBC Television screened a documentary featuring the pair together on his return from Washington.
Sweeney met the world number four when she was 15 and was playing with friends at his club Holywood on the outskirts of Belfast.
On their earlier split he said: "I want to put this time into my golf. You've got to do what's right for yourself."
Their break-up was reported to have shocked family and friends at the time. McIlroy was favourite for last week's event, but his bid to become the youngest Open champion since 1893 ended with him in joint-25th position and sounding doubtful whether he will ever win in bad conditions.
"I'm not a fan of tournaments that the outcome is predicted so much by the weather - it's not my sort of golf," said the 22-year-old. "I'm looking forward to getting back to America and getting back into some nice conditions."