John William Leftwich (September 7, 1826 – March 6, 1870) was an American politician and a member of the United States House of Representatives for the 8th congressional district of Tennessee. He was born in Liberty (now Bedford), Virginia in Bedford County on September 7, 1826. He attended public school, studied medicine, and graduated from Philadelphia Medical College in 1850. He moved to Memphis, Tennessee and engaged in mercantile pursuits.

John Leftwich
Member of the U.S. House of Representatives from Tennessee's 8th district
In office July 24, 1866 – March 3, 1867
Preceded by	James M. Quarles
Succeeded by	David A. Nunn
Personal details
Born	(1826-09-07)September 7, 1826 Liberty, Virginia, U.S.
Died	March 6, 1870(1870-03-06) (aged 43) Lynchburg, Virginia, U.S
Political party	Unconditional Unionist

Upon the readmission of Tennessee to representation, he was elected as an Unionist to the Thirty-ninth Congress. He served from July 24, 1866 to March 3, 1867 and was an unsuccessful candidate for re-election. He was a delegate to the Democratic National Convention in 1868. He was mayor of Memphis in 1869 and 1870. He contested the election of William J. Smith to the Forty-first Congress, but while on his way to Washington to prosecute the contest, he died in Lynchburg, Virginia on March 6, 1870. He was interred in Elmwood Cemetery in Memphis.