One was IMO gold medal winner as well.

*Two IMO gold medal winners. Three ISO gold medal winners. Six ISO gold medals collectively :)

- Yu Deng: IMO gold [1]

- Jacob Tsimerman: 2x IMO gold [2]

- John Pardon: 3x IOI gold [3]

Fun fact: Tsimerman and Deng both overlapped with Peter Scholze (another Fields Medal recipient) at the IMO

[1] https://www.imo-official.org/results/contestant/8824/

[2] https://www.imo-official.org/results/contestant/7387/

[3] https://stats.ioinformatics.org/people/1141