According to event organisers, Mr. Hey from Bracknell in Berkshire required immediate medical attention during the swimming section of the race at Chasewater.
An Ironman Triathlon is a high endurance event consisting of a 2.4-mile swim, a 112-mile bicycle ride and a marathon 26.22-mile run.
It's considered one of the most difficult sporting events in the world.
Almost 3,000 athletes from 55 countries took part in Staffordshire's race.
Mr. Hey was part of a group called the Berkshire Tri Squad, which has since set up a fundraising page to support his family.
In a statement, the chairperson of the organisation Karen Dax said:
"Andy was a vibrant and much loved member of Berkshire Tri Squad and we are devastated to learn of his passing, whilst competing in the sport he loved."We want to honour his memory by supporting the family with a monetary amount for them to decide how to use this. He will be very much missed and all our thoughts are with his family at this difficult time."
Other tributes on the fundraising page include R Barnes who wrote: "So very sorry to hear of Andy’s passing, and my thoughts are with his family (fellow competitor at Staffordshire)."
Mark Wilson added: "Deepest condolences to Andy’s family, thinking of you."
In a statement, Ironman England said: "The athlete was attended to by the on-site medical team before being transported to a nearby hospital where the athlete sadly passed.
"We share our greatest sympathy with the family and friends of the athlete and will continue to offer them our support as they go through this very difficult time.
"We thank the safety personnel and medical staff who worked quickly to provide the athlete with medical support."
To donate, visit the crowdfunding page.