Diomedes may refer to:

• Diomedes, a hero of the Trojan War and king of Argos in Greek mythology
• Diomedes of Thrace, king of Thrace in Greek mythology
• Mares of Diomedes, legendary man-eating horses
• Captain Diomedes, a character in the video games Warhammer 40,000: Dawn of War II – Chaos Rising and Warhammer 40,000: Dawn of War II – Retribution

• Villa of Diomedes, Pompeii, Italy
• Diomede Islands, Russian and U.S. islands in the Bering Strait
• Diomede Bay, Vladivostok, Russia
• 1437 Diomedes, an asteroid

• Diomedes Soter (first century BC), an Indo-Greek king
• Saint Diomedes of Tarsus (died c.300), feast day August 16
• Saint Diomedes, feast day September 2
• Diomedes Grammaticus (4th century), a Latin grammarian
• Diomedes Cato (c.1563–c.1618), a Polish-Italian composer
• Diomedes Maturan (c.1940-2002), a Filipino actor
• Diomedes Komnenos (1956-1973), a Greek student and casualty of the Athens Polytechnic uprising
• Diomedes Díaz (1957–2013), a Colombian vallenato singer and composer

• Diomed, a famous racehorse
• HMS Diomede, Royal Navy ships