Dabney was born in Louisa County on March 5, 1820, the son of Elizabeth Randolph Price Dabney and Charles Dabney, a member of the county court and an elder in the local Presbyterian church. At age seven he began his education in a small log school near his home. He learned Latin from an elder brother and later began to study Greek. Following several months of tutoring in mathematics, Dabney entered Hampden-Sydney College as a sophomore in June 1836. He left after September 1837, returned home to assist his widowed mother, and found time to teach two terms at a local school. In the autumn of 1839 he matriculated at the University of Virginia and in 1842 received an MA.

For the next two years Dabney helped his mother manage the family plantation, taught school, and began his long and productive career as an author by writing articles for Richmond newspapers. Having joined the Presbyterian Church in 1837, he enrolled in November 1844 at the Union Theological Seminary, then affiliated with Hampden-Sydney College. After graduating in June 1846, Dabney returned to Louisa County and preached at Providence Presbyterian Church. On July 16, 1847, he was ordained and installed as minister of Tinkling Spring Presbyterian Church, in Augusta County. Dabney married Margaretta Lavinia Morrison in Rockbridge County on March 28, 1848. Of their six sons, three died as children.

The Union Theological Seminary (later Union Theological Seminary and Presbyterian School of Christian Education) awarded Dabney a doctor of divinity in 1852, and in August of the following year he joined the faculty as professor of church history and church government. In 1859 he took over the duties of the chair of theology and began teaching systematic theology with a rigorous emphasis on Calvinist orthodoxy. The following year he declined offers of a prestigious pulpit in New York and a position on the faculty of Princeton Theological Seminary.

Initially opposed to secession, Dabney sided with his state after Virginia joined the Confederacy in the spring of 1861. In May of that year he began four months of service as chaplain to the 18th Virginia Infantry Regiment before returning to his duties at the seminary. Thomas J. "Stonewall" Jackson often heard Dabney preach during those months and asked Dabney to serve as his adjutant, or chief of staff, a position for which he had neither experience nor skill. Although Dabney preferred resuming the role of chaplain, Jackson was persuasive, and Dabney was commissioned a major, to rank from April 22, 1862. Illness forced him to resign on August 15, but his respect for Jackson never wavered. When Jackson's widow later asked Dabney to write a biography of the general, Dabney threw himself into the effort. His Life and Campaigns of Lieut.-Gen. Thomas J. Jackson (Stonewall Jackson), which highlighted the subject's fervent piety, appeared in a two-volume edition published in London between 1864 and 1866 and a one-volume edition published in New York in 1866.

As soon as his health allowed, Dabney resumed teaching at the Union Theological Seminary. He had been a reluctant secessionist but steadfastly defended the Confederate cause until the day of his death. Terribly embittered by the defeat of the South and by the end of slavery, Dabney was decidedly undemocratic in his politics and racist to the core. He defended an idealized version of the Old South as the very apex of Christian civilization. He spoke and wrote against allowing freedpeople to vote and denounced free public education for blacks and whites. Dabney was as opposed to new theories in science as he was to new ideas about politics, education, and a whole range of so-called progressive concepts, and his Calvinism grew more inflexible as his social and political views calcified. He employed his formidable learning to defend a variety of reactionary causes. From Dabney's pen flowed a series of publications, mounting a rearguard defense of older ways as suggested by the titles: A Defence of Virginia, [and Through Her, of the South] in Recent and Pending Contests Against the Sectional Party (1867), Ecclesiastical Relation of Negroes (1868), A Caution Against Anti-Christian Science (1871), The Sensualistic Philosophy of the Nineteenth Century, Considered (1875), and The Practical Philosophy (1897).

Dabney emerged as one of the most influential leaders of the southern Presbyterian Church. In 1863 he chaired a committee that brought about the merger of new school and old school factions in the South to create the Presbyterian Church in the United States. While serving as moderator of the denominational general assembly in 1870, Dabney helped scuttle efforts to promote fraternal relations between southern and northern Presbyterians, and he vehemently opposed any efforts toward reunification. His essays and sermons appeared frequently in Presbyterian periodicals or in pamphlet form. The publication of his theological texts, Sacred Rhetoric (1870) and Syllabus and Notes of the Course of Systematic and Polemic Theology (1871), both of which went through several editions, ensured that his influence over southern Presbyterian divinity students was unmatched.

Dabney's unhappiness with the postwar situation led him to consider leaving the United States, and in 1883 health problems convinced him to leave Virginia and accept the professorship of moral philosophy at the new University of Texas, in Austin. He liked the climate and at first was optimistic about the prospects for Christian society in Texas, where he helped to found the Austin School of Theology. But modernity soon intruded there, too, and an exasperated Dabney grew ever more embittered. In 1894 the university asked for his resignation, and the following year he and his wife moved to the home of a son in Victoria, Texas.

Though a spirited lecturer and prolific writer, Dabney suffered from ill heath for much of his life, and toward the end his afflictions were multiplied by blindness. He nevertheless saw through to publication Discussions (1890–1897), a four-volume collection of his writings. Dabney died in Victoria, Texas, on January 3, 1898. At his request he was buried at the Union Theological Seminary in Virginia Cemetery, at Hampden-Sydney College.

Major Works

• Life and Campaigns of Lieut.-Gen. Thomas J. Jackson (Stonewall Jackson) (1866)
• A Defence of Virginia, [and Through Her, of the South] in Recent and Pending Contests Against the Sectional Party (1867)
• Ecclesiastical Relation of Negroes (1868)
• Sacred Rhetoric (1870)
• Syllabus and Notes of the Course of Systematic and Polemic Theology (1871)
• A Caution Against Anti-Christian Science (1871)
• The Sensualistic Philosophy of the Nineteenth Century, Considered (1875)
• Discussions (1890–1897)
• The Practical Philosophy (1897)