Lawrence Joseph Jansen (July 16, 1920 – October 10, 2009) was an American right-handed pitcher and coach in Major League Baseball.

In 1940 Jansen was discovered by a scout and started playing for the Salt Lake City Bees, a Class C club at that time.

[1] In 1941, he started playing for the San Francisco Seals in the Pacific Coast League, but in 1943, given the choice between being drafted to fight in World War II or taking a deferment to work on the family dairy farm back in Oregon, he chose the latter.

As an indication of the low salaries of even accomplished players in the mid-twentieth century, Jansen worked in a hardware store in Forest Grove, Oregon, during the off-seasons of his best years.

Arm miseries kept Jansen from a major role in the Giants' 1954 world championship; he spent part of that season inactive, as a coach.

[1][2] Jansen remained as pitching coach for eleven seasons, and helped to develop future Hall-of-Famers Juan Marichal and Gaylord Perry.

He then moved on to his final MLB coaching job, handling pitchers for the Chicago Cubs in 1972–73, working for his old Giants manager, Leo Durocher, and then former teammate Whitey Lockman.

[6] After retiring from baseball, he returned to his hometown Verboort, Oregon, where he sold real estate and lived the remainder of his life in the house he had built in 1951.