Silas Seth "Sox" Griffis (September 22, 1883 – July 9, 1950) was a Canadian athlete of the early 20th century. In ice hockey, Griffis was a two-time Stanley Cup winner, with the 1907 Kenora Thistles and the 1915 Vancouver Millionaires. He is an inductee of the Hockey Hall of Fame.
Born in Onaga, Kansas, Griffis moved with his family to Rat Portage, Ontario, Canada, where he excelled in many sports, including ice hockey. It was here that he became a player for the local amateur hockey club, the Rat Portage Thistles.
Notable for his speed, Griffis played both rover and cover-point in the seven-man configuration of the day, and led the Thistles to league titles in 1903 and 1905, as well to a Stanley Cup challenge in 1905 against the powerful Ottawa Silver Seven. Griffis scored three goals in the three game series, although the Thistles lost to Ottawa.
Now renamed the Kenora Thistles, the team remained a powerhouse, and Griffis was a key member of the Thistles' January 1907 Stanley Cup winning team when they defeated the Montreal Wanderers in a two-game total goal series. The Wanderers, however, issued a second challenge for the cup in March 1907, which the Thistles lost.
He later played for the Vancouver Millionaires of the Pacific Coast Hockey Association starting in 1912, moving back to defence and was team captain in 1914–15, the year the Millionaires themselves won the Cup. Griffis injured his leg that season and was not able to play in the championship. The leg did not heal well and Griffis' ice time declined until he finally retired from professional hockey in 1919.
Griffis played in 154 senior matches, scoring 84 goals.
In later life, Griffis excelled as both a competitive golfer and bowler. He was elected to the Hockey Hall of Fame in July 1950. He died in Vancouver, British Columbia, that same month. He is also a member of the Northwestern Ontario Sports Hall of Fame.