Year 419 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Tribunate of Lanatus, Rutilus, Tricipitinus and Axilla (or, less frequently, year 335 Ab urbe condita). The denomination 419 BC for this year has been used since the early medieval period, when the Anno Dominicalendar era became the prevalent method in Europe for naming years.
Despite the Peace of Nicias still being in effect, Sparta's King Agis II gathers a strong army at Philus and descends upon Argos by marching at night from the north. His allied Boeotian forces fail him, but he is able to conclude a treaty with Argos.