The condition is extremely rare, reports The Independent. About one in six million is born with so-called diphallia, two penises, and three penises are even more rare.
Triphallia has only been reported once before, in a newborn boy in Iraq in 2020.
The new discovery, described in a study published in Journal of Medical Case Reports, was made during the dissection of a 78-year-old man.
According to the study, it is possible that the man never realized he had three penises, as the other two were smaller and hidden behind the primary genital organ.
Researchers at the University of Birmingham suspect that more men than expected may have three penises – without knowing it.
"Without dissection, this anatomical variation would have remained undetected, which suggests that the prevalence of polyphallia is greater than expected," they write.