Christopher St. John "Sinjin" Smith (born May 7, 1957 in Santa Monica, California) is a professional beach volleyball player. He won one U.S. championship and two World championships with Randy Stoklos.

He began to compete as a professional in the two man beach volleyball tournaments of Southern California at age fifteen. In 1977 he won his first tournament, teaming with "Stormin" Mike Normand. He went to college at UCLA, where he played volleyball as a setter and outside hitter under head coach Al Scates. The UCLA Bruins won the national championship in Smith's freshman year. Smith contributed more substantially in the 1978 run, where the Bruins reached the finals before losing to Pepperdine.

In 1979 the Bruins defeated cross town rival USC to win the national championship. Smith received All American honors both years. In the early 1980s he made a successful beach team pairing with former UCLA teammate Karch Kiraly. They split up after Karch began focusing on the National Olympic Team. He moved on to partner with Randy Stoklos, and the two became the most dominant pair in men's beach volleyball. Smith was the first player to reach 100 career open tournament wins. He was a primary force behind the growth of beach volleyball as a sport, and the development of the Association of Volleyball Professionals, which formalized the sport as a professional athletic competition.