Justin Thomas has said sorry after on-course microphones captured him using a homophobic slur during the third round of the Sentry Tournament of Champions in Hawaii.
The incident occurred after the world No.3 missed a short putt for par on the fourth hole at Kapalua's Plantation Course. As he stood over a tap-in for bogey, he could be clearly heard uttering the remark to himself.
Afterwards, 27-year-old Thomas apologised, described his comment as "inexcusable".
"There's no excuse," he said. "I'm an adult. I'm a grown man. There's absolutely no reason for me to say anything like that.
"It's terrible. I mean, I'm extremely embarrassed. It's not who I am, it's not the kind of person that I am or anything but, unfortunately, I did it and I have to own up to it and I'm very apologetic."
Thomas said that he was initially unaware that he had made the remark and it was only after completing his round that it was brought to his attention.
"I'm speechless," he added. "It's bad. There's no other way to put it.
"I need to do better. I need to be better. It's definitely a learning experience, but, yeah, I just, I deeply apologise to everybody and anybody who I offended and I'll be better because of it."
In a statement obtained by Golf Digest, a PGA Tour spokesperson said: "As he expressed after his round, we agree that Justin’s comment was unacceptable."
It is unclear what sanctions - if any - Thomas will face. The PGA Tour does not disclose details of disciplinary action it takes against its members.