Apostolos Christou (Greek: Απόστολος Χρήστου; born 1 November 1996) is a Greek swimmer specializing in backstroke. He is the Greek National Record holder in the 100 metre freestyle and 50, 100, and 200 metre backstroke events, as well as contributing to national record efforts in the 4x100 metre freestyle and medley relays. He is a three-time Olympian, qualifying in 2016, 2021, and most recently 2024, where he became Greece's first Olympic medalist in swimming since the inaugural 1896 Games through his 2nd place finish in the 200 metre backstroke.

2013 marked then-16-year-old Christou's first major successes at an international stage. At the 2013 European Junior Swimming Championships, Christou placed 3rd in the 50 metre backstroke, his first medal finish at a major competition outside his home country, Greece. Then, at the 2013 World Junior Championships, Christou placed first in 54.87, beating 2nd place Danas Rapsys by 0.37 seconds. He also placed 9th in the 50 metre backstroke semifinal (26.18) and 14th in the semifinal of the 200 metre (2:04.20).

At the European Junior Swimming Championships in July 2014, Christou again competed in all three backstroke distances, placing in the top two of all three events.

On the first night of the meet in the 100 metre backstroke semifinals, Christou set a new world junior record with a time of 54.41. This time was over a second slower than the 53.38 set by then-17-year-old Ryan Murphy at the 2013 US National Championships; however, FINA only started tracking this record in April 2014 and established the records as the winning time from the 2013 World Junior Championships, so the previous record to beat was not Murphy's time but rather Christou's own 54.87. This swim also made Christou the top seed heading into finals, where he again placed first with another world junior record, this time swimming a 54.03 and beating Italian Simon Sabbioni (54.25) and Russian Evgeny Rylov (54.46) for gold.

Later in the meet, Christou won silver in both the 50 metre backstroke (25.33) and the 200 metre backstroke (1:59.77).

In August, Christou competed at the 2014 Youth Olympic Games, where he placed 2nd in the 50 metre backstroke (25.44) and 4th in the 100 metre backstroke (55.06), exactly half a second off the podium. Notably, his 54.03 from the month prior would have won him gold, as Rylov and Sabbioni tied for first with a time of 54.24. Christou also competed in the 200 metre backstroke, where he placed 13th in the semifinals in a time of 2:04.45.

In August 2015, Christou made his senior international debut at the 2015 FINA World Championship, although he failed to advance past the heats in all of his events. He placed 24th in the 50 metre backstroke (25.50) and 31st in the 100 metre backstroke (55.10) in addition to leading off the 4 x 100 metre medley relay in a time of 55.43. He was also entered in the 200 metre backstroke, although he did not swim in the heats.

In May 2016, Christou again competed in the 50, 100, and 200 metre backstrokes in addition to the 4x100 metre freestyle and medley relays. In finals, he tied for 3rd in the 100 (54.19) and 5th in the 200 (1:58.87). He swam significantly faster in earlier rounds, however; his prelims and semifinals times of 53.77 and 53.36 in the 100, respectively, were both faster than Camille Lacourt's gold medal–winning time of 53.79 in finals, and he swam a 1:57.41 in semifinals of the 200 metre, which would have placed 4th. Still, these earlier swims all marked significant personal bests for Christou, as he won his first senior international medal, bronze. He also placed 10th in the semifinal of the 50 metre backstroke (25.28).