Robert Marshall (January 2, 1901 - November 11, 1939) was an American forester, writer, conservationist and wilderness activist and explorer. Known for his enthusiasm and strong personality, he was a supporter of socialism and civil liberties. The son of wealthy constitutional lawyer and early wilderness advocate Louis Marshall, Marshall was exposed to nature as a young child. He quickly developed a love for the outdoors, becoming one of the first three people—alongside his brother George and their guide—to climb to the summits of the 46 major peaks of the Adirondack Mountains in northeastern New York. He also traveled to the Alaskan wilderness and compiled numerous articles and publications, including the 1933 bestselling book Arctic Village, based on his time in Wiseman, Alaska.

A scientist with a Ph.D in plant physiology, Marshall devoted considerable energy to defining wilderness as a social as well as an environmental ideal. He was the first to suggest a formal, national organization of individuals dedicated to the preservation of primeval land. One of the principal founders of The Wilderness Society, he also held two important public posts—chief of forestry in the Bureau of Indian Affairs from 1933 to 1937 and head of recreation management in the Forest Service from 1937 to 1939. 25 years after Marshall's death at the age of 38, The Wilderness Society became responsible for passing the Wilderness Act, which legally defined the wilderness of the United States and protected some nine million acres (36,000 km²) of federal land. The Bob Marshall Wilderness in Montana was named in his honor.

Robert James Percival Marshall, OAM, (born in Kalgoorlie in 10 April 1910; died in Perth on 23 February 2004) was a notable Australian amateur player of English billiards, who won the World Amateur Billiards Championship in 1936, 1938, 1951 and 1962 and was runner-up three times, as well as a national snooker champion.

Marshall was born in the same town as another legend of the game, Walter Lindrum. Throughout his career he was compared favourably with Lindrum who, in 1954, himself declared that Marshall was one of the greatest amateur players he had ever seen. Ten years later, the contemporary English snooker professional Fred Davis said of Marshall, "Most noticeable about his style is his compactness, so like Walter Lindrum, and the shortness of his back-swing, hardly more than a couple of inches."