"Only Nineteen", "I Was Only Nineteen" 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 forty 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 infantry regular soldiers experience in the Vietnam War, from training in Australia to first hand exposure to military operations and combat, and ultimately his return home disillusioned, psychologically scarred and possibly suffering from the effects of the chemical defoliant Agent Orange.

Contrary to popular belief, the subject of this song is a volunteer member of the Australian Army, and not a conscript. Australian men did not become eligible for conscription until the age of 21.

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 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." — John Schumann

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.

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