Arthur Lanigan-O'Keefe has confirmed he will have to miss this summer's Olympic Games.
The pentathlete has failed to recover in time from a hip injury.
Lanigan-O'Keefe represented Ireland at Rio 2016, finishing 8th overall. Four years prior in London he'd placed 25th.
The 29-year old had qualified for his third Olympic Games, but his place will instead go to Mexico's Alvaro Sandoval Aguilar.
Natalya Coyle has been selected to represent Ireland at what will be third third Olympics.
Last month saw the injury force Lanigan-O'Keefe out of the final of the UIPM 2021 Pentathlon World Cup final in Hungary.
"My injury to my hip is too much to overcome and I have decided that the honourable thing to do would be to pass my place onto another athlete who was fit to compete at the highest level," Lanigan-O'Keefe wrote on Instagram.
"This is not a decision I have taken lightly and it’s been one of the most painful things for me to do having fought soo hard to get here.
"I made my intentions for Tokyo very clear and that was to go competing for a medal.
"This is no longer possible with my injury, so to travel and not represent myself or my country to the fullest would be dishonourable and in my opinion against the core values of Olympism which are “excellence, friendship and respect”.
Lanigan O'Keefe added, "Thank you everyone for your support over the past few weeks.
"It has been almost overwhelming and something I honestly didn’t expect.
"I just want to say everyone of those messages made a difference and I appreciate you all for that. I am doing good and now focusing my energy into helping my beautiful fiancé Natalya Coyle reach the top of that podium for both of us."