John Gould Stephenson (March 1, 1828 – November 11, 1883) was an American physician and soldier who served as Librarian of Congress from 1861 to 1864. Born in Lancaster, New Hampshire, to a prominent merchant family, he attended the Dartmouth Medical College and Castleton Medical College, where he received his M.D in 1849. Stephenson moved to Terre Haute, Indiana, in the early 1850s, where he became active in the temperance movement and the nascent Republican Party. He campaigned for Abraham Lincoln in the 1859 Senate race in Illinois and the 1860 presidential election. He pursued an appointment as Librarian of Congress immediately following Lincoln's election, possibly due to his brother's work as a librarian in Cincinnati. After a lengthy pressure campaign from prominent Republicans, Lincoln appointed Stephenson as Librarian of Congress, replacing long-term incumbent John Silva Meehan despite opposition from the Joint Committee on the Library.

Believing the library had fallen into neglect under Meehan's administration, Stephenson began a mass change of staff soon after taking office, firing all but one assistant. He hired journalist Ainsworth Rand Spofford, a friend of his brother, as assistant librarian in August 1861. Although never formally commissioned, Stephenson began serving in the Union Army soon after his appointment as Librarian of Congress. He briefly served as an acting naval surgeon to the 19th Indiana Infantry in 1861, before serving as an aide-de-camp in the Indiana militia, where he achieved the rank of colonel. In 1863, he served as the aide-de-camp of Solomon Meredith, commander of the Iron Brigade, and saw action at the battles of Chancellorsville and Gettysburg. He resigned as librarian for unclear reasons in December 1864, and was succeeded by Spofford. He served in various positions as a legal clerk during the 1870s, and was appointed as a medical examiner at the Bureau of Pensions in Washington in the early 1880s. He died after a period of illness and was buried in the Congressional Cemetery.

On March 1, 1828, John Gould Stephenson was born in Lancaster, New Hampshire, to Reuben and Mary King Stephenson (née Baker), the fourth of eight children. Reuben Stephenson was a merchant who operated a general store in Lancaster, additionally serving as a selectman, county coroner, deputy sheriff, constable, fire warden, and high sheriff. Other members of the Stephenson family were elected to a variety of local civic positions. John Stephenson attended school at the Lancaster Academy, which his father had co-incorporated in 1828. Stephenson was active in theater at the academy, performing in a variety of plays. He initially pursued further education at Dartmouth Medical School before transferring to Castleton Medical College, where he received his Doctor of Medicine on November 23, 1849.

The 1850 census lists Stephenson as a physician in Lancaster, but it is unclear if he ever practiced medicine in the town. He likely moved to Terre Haute, Indiana, in 1851, where he worked as a physician and surgeon. While in Terre Haute, he became involved with the temperance movement, joining the local Sons of Temperance chapter, as well as with the nascent Republican Party. He campaigned on behalf of Abraham Lincoln in the 1859 Senate race in Illinois against Stephen Douglas, where Stephenson was described as an "efficient speaker" by Indiana politician William P. Dole.

Stephenson was one of Lincoln's earliest advocates for the 1860 Republican National Convention in Chicago, writing in support of his candidacy in March 1860. At the convention, he worked to influence the Kentucky delegation into supporting Lincoln. He campaigned for Lincoln in both Indiana and Illinois, writing that he spent several weeks campaigning for him in Clark County and Edgar County, Illinois.

Shortly after Lincoln's victory in the presidential election, Stephenson began to pursue a political appointment as the librarian of Congress, using connections within the Republican Party. His brother, Reuben Henry Stephenson, worked as the librarian of the Young Men's Mercantile Library of Cincinnati, and this may have influenced him to pursue the position. Many testimonials in favor of appointing Stephenson to the position were sent to Lincoln, beginning within a few weeks after the election. Various figures, including local physicians and a Kentucky Republican convention delegate, wrote to Lincoln, emphasizing Stephenson's service to the Republican Party and the Lincoln campaign. In March 1861, Senator Henry S. Lane wrote to Lincoln in support, stating that Stephenson was a "gentleman of fine education" and that his appointment would "give great pleasure to the Republicans of his neighborhood". At least one other candidate, Hezekiah Lord Hosmer, ran for the position.

Stephenson arrived in Washington, D.C., at some point before May 1861 and wrote a letter to Lincoln asking to be appointed, urging haste so as to become acquainted with the library before the opening of the next session of Congress. Dole, Lincoln's Commissioner of Indian Affairs, described meeting with Lincoln to urge Stephenson's appointment:

I have just left Mr. Lincoln. I found him alone this evening and had a good old fashioned talk as I frequently have and always, when he has leisure ... Mr. Lincoln is very kind to me and has given me not only what I have asked for myself but so far nearly anything I have asked for my friends ... and promised me to appoint Dr. Stevenson Congressional Librarian tomorrow. You know that the Dr. is not heavy mettal [sic] but he has worked hard for us & is poor and can hand down books to M. C. as well & as gracefully as any one and besides he is a Wabash man and I am for him. You know I never forget friends.