The men's marathon T12 event at the 2020 Summer Paralympics in Tokyo, took place on 5 September 2021.

The T12 category is for athletes with visual impairment.

Athletes in this category will generally have some residual sight, the ability to recognise the shape of a hand at a distance of 2 metres and the ability to perceive clearly will be no more than 2/60.

T12 athletes commonly run with guides.

Prior to the competition, the existing records were as follows:[1] The race took place on 5 September 2021, at 6:50:[2]