Antoninus Pius (Latin: Titus Aelius Hadrianus Antoninus Pius; 19 September 86 – 7 March 161) was Roman emperor from 138 to 161. He was the fourth of the Five Good Emperors from the Nerva–Antonine dynasty. Antoninus was an effective administrator, leaving his successors a large surplus in the treasury, expanding free access to drinking water throughout the Empire, encouraging legal conformity, and facilitating the enfranchisement of freed slaves. He died of illness in 161 and was succeeded by his adopted sons Marcus Aurelius and Lucius Verus as co-emperors.