Jonathan Tan Eu Jin (born 11 March 2002)[1] is a Singaporean swimmer.

He represented Singapore at the 2019 World Aquatics Championships held in Gwangju, South Korea and he finished in 34th place in the heats in the men's 50 metre freestyle event.

[4] During the 16th Singapore National Swimming Championships Invitationals in 2021, Tan broke his own national record for the men’s 50m freestyle with 22.12 seconds[5] and qualified for the 2021 Southeast Asian Games (SEA Games).

[6] Tan won the men's 200m freestyle event with 1 min 50.17 seconds but failed to qualify for both 2021 SEA Games and the 2020 Summer Olympics.

He graduated from Anglo-Chinese School (Independent) with an International Baccalaureate diploma.