William Parker Caldwell was an American politician and a member of the United States House of Representatives for the 9th congressional district of Tennessee.
He was born in Christmasville, Tennessee in Carrol County on November 8, 1832. He attended school at McLemoresville, Tennessee and at Princeton, Kentucky. He studied law at Cumberland School of Law at Cumberland University in Lebanon, Tennessee and was admitted to the bar in 1853. He practiced in Dresden and Union City, Tennessee.
William Caldwell served in the Tennessee House of Representatives from 1857 to 1859. He was a presidential elector on the Democratic ticket of Douglas and Johnson in 1860. He was a delegate to the Democratic National Convention in 1868. He was elected as a Democrat to the Forty-fourth and Forty-fifth Congresses. He served from March 4, 1875 to March 3, 1879, but he was not a candidate for re-election to the Forty-sixth Congress in 1878. He resumed the practice of law in Gardner, Tennessee and served in the Tennessee Senate from 1891 to 1893. He died in Gardner, Tennessee on June 7, 1903. He was interred in Caldwell Cemetery.