Marcus Horatius Turrinus Barbatus (fl. c. 450–449 BC) was a Roman senator from the early Republic, who served as consul in 449 BC alongside Lucius Valerius Poplicola Potitus. According to Roman historical tradition, he and Valerius played an important role in ending the Decemvirate and bringing harmony between the patrician and plebeian orders. To the two consuls are traditionally attributed the Valerio-Horatian Laws, which gave full force of law to measures passed by plebiscite, restored the right of any citizen to appeal to the people, and confirmed the sacrosanctity of plebeian tribunes. The historicity of these laws has been doubted.