Damian David George Warner is a Canadian track and field athlete specializing in decathlon. He is the 2020 Olympic champion and a four-time World medallist. Warner also won the bronze medal at the 2016 Summer Olympics and was the 2014 Commonwealth champion and the two-time and reigning Pan American champion from the 2015 and 2019 Games. Warner holds the Pan Am Games record and the Canadian record for the decathlon and the fourth-highest decathlon score in history. Warner also holds the Olympic Games Record for the Decathlon at 9018 points. Competing in the heptathlon, he is the 2022 World Indoor champion.

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.