Antonia "Tonia" Machaira (Greek: Αντωνία "Τόνια" Μαχαίρα; born May 21, 1971) is a retired Greek swimmer, who specialized in sprint and middle-distance freestyle events. She represented Greece in two editions of the Olympic Games (1996 and 2000), and later helped the Greeks capture the silver medal in the freestyle relay (3:48.74) at the 2001 Mediterranean Games in Tunis, Tunisia. At the 2001 Mediterranean Games in Tunis, Tunisia, Machaira helped the Greeks captured a silver medal in the 4 × 100 m freestyle relay with a sterling time of 3:48.74.