Howe retired for the first time in 1971 and was immediately inducted into the Saskatchewan Sports Hall of Fame that same year. He was then inducted into the Hockey Hall of Fame the next year, but came back two years later to join his sons Mark and Marty on the Houston Aeros of the WHA. Although in his mid-40s, he scored over 100 points twice in six years, won two straight Avco World Trophies (1974 and 1975) and was named most valuable player in 1974. He made a brief return to the NHL in 1979–80, playing one season with the Hartford Whalers, then retired at age 52. His involvement with the WHA was central to their brief pre-NHL merger success, forcing the NHL to recruit European talent and expand to new markets.
How many times did Gordie Howe retire?
Based on the provided information, Howe retired two times.

Howe retired for the first time in 1971, but then later joined his sons Mark and Marty on the Houston Aeros of the WHA. Howe would then return to the NHL in 1979 where he played one season before retiring for a second time.