"Only 19", "I Was Only 19" or "A Walk in the Light Green" is the most widely recognised song by Australian folk group Redgum. The song was released in March 1983 as a single, which hit number one on the national Kent Music Report Singles Chart for two weeks. It was also recorded for Redgum's live album Caught in the Act (Epic Records) released in June, which stayed in the top 40 of the Kent Music Report Albums Chart for four months. Royalties for the song go to the Vietnam Veterans Association of Australia. It is in the Australasian Performing Right Association's Top 30 Australian Songs of all time.

The song is a first-person account of a typical Australian soldier's experience in the Vietnam War, from training at a military academy in Australia to first hand exposure to military operations and combat, and ultimately his return home disillusioned and suffering from both PTSD and, it is implied, the harmful effects of Agent Orange.

Redgum's lead vocalist-guitarist, John Schumann, wrote the song based on experiences he heard from veterans, particularly Mick Storen (his brother in-law) and Frankie Hunt. The mine experiences in the story pertain to an incident during Operation Mundingburra on 21 July 1969 of which Storen experienced. Schumann has said that "the power derives from the detail, provided by my mate and brother-in-law, Mick Storen, who was brave and trusting enough to share his story with me."

For the live version, Schumann explained the title, "A Walk in the Light Green", as referring to operational patrols in areas marked light green on topographical maps, where dark green indicated thick jungle, plenty of cover and few land mines and light green indicated thinly wooded areas, little cover and a high likelihood of land mines.

In January 2018, as part of Triple M's "Ozzest 100", the 'most Australian' songs of all time, "I Was Only 19" was ranked number 20.