William Lowell Putnam III
William Lowell Putnam III  (born 1924) is an alpinist, author and retired broadcasting executive. He is also sole trustee of the Lowell Observatory, a private astronomical research facility; the son of Roger Putnam and a member of the once-prominent Lowell family of Massachusetts. 
Over several decades beginning in the 1940s, Putnam made many first ascents and difficult exploratory expeditions centered in the Selkirk Mountains of British Columbia.
After serving as the American Alpine Club guidebook editor for western Canada beginning in 1957 and subsequently in other capacities, Putnam was the club's president from 1971-73. Related to these activities, Putnam was U.S delegate to the International Mountaineering and Climbing Federation (or UIAA) for 30 years, and for much of this period also represented Canada.
The construction of three mountain cabins in western Canada now operated for the public by the Alpine Club of Canada was spearheaded and completed by Putnam. One of these accommodations, in the northern Columbia, or Selkirk Mountains, was renamed the Bill Putnam Hut in 2002 by the Alpine Club of Canada to recognize his contribution to Canadian mountaineering.
Putnam studied geology at Harvard University and later was founder and chief executive of the Springfield Television Corp. (Massachusetts), a company which he sold in 1984. During World War II, he was wounded in combat. 
Among his books are A century of American Alpinism, as well as K2: The 1939 Tragedy, and a biography of Swiss-Canadian mountain guide Ed Feuz (the last two together with Andrew J. Kaufman) as well as A Yankee Image: The Life and Times of Roger Lowell Putnam.
- International Mountaineering and Climbing Federation (UIAA). "William Lowell PUTNAM". theuiaa.org. Retrieved 2011-07-04.
- "Lowell Observatory". Lowell.edu. Retrieved 2011-07-04.
- Selkirk guidebooks (North & South editions); Elaho Publishing, Squamish, B.C.; see sections on climbing history
- "Alpine Club of Canada - Clubhouse and Mountain Huts / Bill Putnam (Fairy Meadow) Hut". Alpineclubofcanada.ca. Retrieved 2011-07-04.