Francis Gibbons "Frank" Tatnall (1896–1981) was an American engineer and entrepreneur, known as the "father of the strain gage." He was the son of William Francis Tatnall (1862-1913) and Lillian Harriett Runcie Tatnall (1862-1958). He graduated in 1918 from the University of Pennsylvania with a bachelor's degree in mechanical engineering.

Tatnall worked for Baldwin-Southwark Corporation, a subsidiary of Baldwin Locomotive Works, selling test equipment. In 1951, Baldwin Locomotive Works merged with the Lima-Hamilton Corporation to form Baldwin-Lima-Hamilton Corporation, where Tatnall was manager of testing research. During the mid-1950s, the Budd Company of Philadelphia established a new division called Tatnall Measuring Systems (TMS), focusing on advanced equipment and materials testing. Tatnall served as director, general manager, and vice president. Following his retirement from TMS, Tatnall joined Vishay Intertechnology, Inc., a manufacturer of discrete semiconductors and passive electronic components, where he worked until his death in 1981.

Tatnall was named the first honorary member of the Society for Experimental Stress Analysis (later the Society for Experimental Mechanics) in 1951. The society initiated the F.G. Tatnall Award in his honor in 1967 to recognize individuals who have made outstanding service contributions to the society, with Tatnall being the inaugural recipient in 1968. The University of Pennsylvania Department of Mechanical Engineering and Applied Mechanics awards the Francis G. Tatnall Prize to seniors; the Francis G. Tatnall Laboratory was dedicated in 1977.

Tatnall married Amelie d'Auquetil Vauclain (1907-2004) in 1928; the couple had four children.