Ireland centre Jared Payne has been forced to retire due to the concussion sustained on the 2017 British and Irish Lions tour to New Zealand.
The 32-year-old will take up the role of defence coach with Ulster, the province he represented 78 times alongside an international career that numbered 20 caps.
He has not played since his try-scoring performance against the Chiefs in June last year that ended when a head knock resulted in his substitution, ushering in the onset of persistent symptoms that have continued into 2018.
"It's been a good ride but unfortunately every good thing has to come to an end," Payne said.
"Playing rugby has taken me to places I never thought I'd see and allowed me meet people I never thought I'd meet.
"While I will undoubtedly miss the buzz of running out with mates every weekend, I have to listen to the medical advice and unfortunately give up the dream."
Payne, who is originally from Tauranga in New Zealand, is to work alongside Ireland's coaching team during next month's tour to Australia.