Hartshorne (pronounced "Hearts-orn") is a city in Pittsburg County, Oklahoma, United States. It is the third largest city in the county. The population was 1,947 at the time of the 2020 United States census.

The community was named for Dr. Charles Hartshorne, a wealthy investor from Philadelphia, Pennsylvania, who was attracted by the potential profits offered by coal deposits in the area.

The present-day city of Hartshorne began as a coal mining community about 1850. Coal mine operators in the Indian Territory recruited European immigrants to work the mines. The first workers were probably English and Irish, but other ethnic groups soon joined them. These included Italians and eastern Europeans. Like many other such communities, this was a company town, built very close to the mine, with rudimentary houses and a company store.

A post office opened at Hartshorne, Indian Territory on March 5, 1850. It was named for Dr. Charles Hartshorne, a railroad official. Jones Academy was established southwest of Hartshorne in 1881. At the time of its founding, Hartshorne was located in Gaines County, a part of the Moshulatubbee District of the Choctaw Nation.

The Choctaw Coal and Railway (CC&R) line, acquired by the town, was incorporated in 1887 and began building a 67 miles (108 km) line between Wister and South McAlester. In 1894, the CC&R was reorganized and renamed the Choctaw, Oklahoma and Gulf Railroad (CO&G) in 1894. The Wister - South McAlester line was completed in 1900, and also linked to Wilburton, Alderson and Hartshorne. In 1902, the Chicago, Rock Island and Pacific Railway gained control of the CO&G. In 1904 an electric interurban began service from McAlester to Hartshorne.

The Holy Rosary Church, complete with a rectory, a convent, and a parochial school, was built in 1895 by Russian and other Eastern European immigrants. Other churches constructed before the 20th Century were: Baptist, Methodist, Christian, Presbyterian, and Episcopal. The Saints Cyril and Methodius Russian Orthodox Greek Catholic Church remains a town landmark and is included on the National Register of Historic Places listings in Pittsburg County, Oklahoma. Completed in 1916, it replaced an earlier 1897 version that immigrants from Russia and other eastern European countries constructed.

The Saints Cyril and Methodius church had been owned by the Sts. Cyril Methodius Orthodox Church, Inc. On March 20, 2016, a man named Bill Melancon filed a quitclaim deed in the Pittsburg County Clerk's office, transferring ownership of the property to Melancon. The quitclaim deed had been signed by Bill O'Nesky, a church member, who Melancon claimed was a church trustee. Melanin also presented a Special Warranty Deed dated in 2010, by Bill O’Nesky, Tanya O’Nesky, and Foy Ledbetter, identified as successor trustees of the church. A group of church members first learned about the alleged sale soon afterward, when they found strangers on and inside the property. They filed suit in District Court. The case came before Judge James Bland in April 2016. Judge Bland issued a restraining order to bar Melancon, his agents and representatives from coming on or within 100 yards (91 m) of the property, or removing anything or making any changes before Bland revisited the case in June 2010. An out of court settlement between the church members before the date set by the judge resulted in the dismissal of the case, and a deed signed by Melanin transferring ownership back to the church.

The community incorporated in Tobucksy County of the Choctaw Nation by order of the U.S. District Court, Central District, Indian Territory, on March 1, 1900. Hartshorne became part of Pittsburg County at statehood on November 16, 1907.