Romanchuk entered and finished the
Baltimore Marathon, his first, at the age of 14. In April 2018, he placed 3rd in the
London Marathon. In October 2018, Romanchuk won the
Chicago Marathon with a time of 1:31:34; he beat defending champion
Marcel Hug by one second. Less than a month later, he became the first American winner and youngest winner in the history of the New York Marathon's wheelchair event, again defeating Hug (who had won in 2016 and 2017), and again by just one second. In 2019, Romanchuk won the
Boston Marathon in 1:21:36. He became the youngest ever winner of that race, as well as the first American to win Boston since 1993. In April 2019, he won the London Marathon with a time of 1:33:38. In 2019 he also won the
Chicago Marathon and he qualified to
represent the United States at the
2020 Summer Paralympics held in Tokyo, Japan. He won the bronze medal in the
men's marathon T54 event. In October 2022, Romanchuk placed second in the
2022 London Marathon, with a time of 1:24:40, two seconds behind Hug. In November 2024, Romanchuk secured his third victory in the men’s wheelchair division of the
New York City Marathon, finishing 5 seconds ahead of
David Weir and completing the race in a time of 1:36:31. He had previously won the race in 2018 and 2019. ==References==