Three-time world champion and Olympic silver medallist Kelly Catlin has died aged 23, USA Cycling has confirmed.
Catlin won three straight team pursuit world titles on the track from 2016 to 2018, claiming silver in the same event at the Rio 2016 Games.
She competed for Rally UHC Cycling on the road and was studying for a graduate degree at Stanford University.
"We are deeply saddened by Kelly's passing," said USA Cycling president and chief executive Rob DeMartini.
In a letter to VeloNews Catlin's father Mark said that his daughter had taken her own life.
"We will all miss her dearly," added DeMartini. "Kelly was more than an athlete to us and she will always be part of the USA Cycling family.
"Our thoughts and prayers are with the Catlin family. This is an incredibly difficult time and we want to respect their privacy.
"The entire cycling community is mourning this immense loss. We are offering continuous support to Kelly's team-mates, coaches and staff. We also encourage all those who knew Kelly to support each other through the grieving."
Catlin also won individual pursuit bronze at both the 2017 and 2018 World Track Championships.
She won all three of her world titles alongside Chloe Dygert Owen and Jennifer Valente, while Kimberley Geist was part of the 2017 and 2018 triumphs after Sarah Hammer rode in 2016.
Catlin, who was born in Saint Paul, graduated from the University of Minnesota last year with degrees in mathematics and Chinese and was studying computational and mathematical engineering at Stanford University in California.
"The news of Kelly's passing has hit the team hard," said Rally UHC Cycling in a statement on social media.
"Losing an incredible person at such a young age is very difficult.
"Kelly was our friend and team-mate. Our heartfelt condolences go out to her family and those who were fortunate enough to know her best."
Chloe Dygert Owen, who was in the same team for all three of Catlin's world titles, posted on social media: "We will miss you forever. Rest in peace now, Kelly."
Three-time Olympic time trial champion Kristin Armstrong also posted: "This is a devastating loss. We need to continue to look after our cycling family. RIP Kelly. I'll always remember your sense of humour, wit and kindness."
In a piece Catlin wrote two weeks before her death, she described the stress of working as a pro racer while studying in university as similar to "juggling knives".
"Being a graduate student, track cyclist, and professional road cyclist can instead feel like I need to time-travel to get everything done. And things still slip through the cracks," she wrote.
"So how do I balance three competing (no pun intended) careers?
"Easy. I don't balance them."