One in six men are unaware they have a prostate - meaning they risk missing signs of cancer.
Polling for the charity Prostate Cancer UK also found more than half of men do not know where the prostate gland is and only one in 12 know what it does.
The gland is the size of a walnut and sits beneath the bladder. It plays a key role in sex, making the fluid that sperm swim in. But it can also be home to the leading type of cancer among men, with 47,000 diagnoses and 10,900 deaths each year.
The charity's Angela Culhane said: "Ignoring your prostate can be lethal ... and shockingly many men only realise they have a prostate when it starts to go wrong ... we need to wake up and stop men dying needlessly."
Symptoms include need to urinate frequently, difficult or painful urination, and blood in urine.