Laurence Henry "Dutch" Rennert, Jr. (born June 12, 1930 in Oshkosh, Wisconsin) is a former umpire in Major League Baseball who worked in the National League from 1973 to 1992. He was considered one of the game's most colorful characters, best known for his animated and loud strike calls; similar to the NFL's colorful referee Red Cashion. A 1983 New York Times poll resulted in his selection as the NL's best umpire. He wore uniform number 16 throughout his career.
Reaching the major leagues after umpiring in the Pacific Coast League from 1965 to 1973, Rennert umpired in six National League Championship Series (1977, 1981, 1982, 1986, 1988, 1990), two All-Star Games (1979, 1984), and three World Series (1980, 1983, 1989); he was behind the plate when the Oakland Athletics clinched the 1989 World Series title.