The men's decathlon competition at the 2016 Summer Olympics in Rio de Janeiro, Brazil. The event was held at the Olympic Stadium between 17 and 18 August.

The decathlon is a combined event in athletics consisting of 10 track and field events. The word "decathlon" was formed, in analogy to the word "pentathlon", from Greek δέκα and ἄθλος. Events are held over two consecutive days and the winners are determined by the combined performance in all. Performance is judged on a points system in each event, not by the position achieved. The decathlon is contested mainly by male athletes, while female athletes typically compete in the heptathlon.