Henri Grégoire (often referred to as Abbé Grégoire; December 4, 1750 – May 20, 1831) was a French Roman Catholic priest, constitutional bishop of Blois and a revolutionary leader.

He was elected in 1789 by the clergy of the bailliage of Nancy to the Estates-General, where he soon made his name as one of the group of clerical and lay deputies of Jansenist or Gallican sympathies who supported the Revolution. He was one of the first of the clergy to join the third estate, and contributed notably to the union of the three orders; he presided at the session which lasted sixty-two hours while the Bastille was being attacked by the people, and spoke vehemently against the enemies of the nation. He later took a leading role in the abolition of the privileges of the nobles and the Church.

Under the new Civil Constitution of the Clergy, to which he was the first priest to take the oath (December 27, 1790), he was elected bishop by two départements. He selected that of Loire-et-Cher, taking the old title of bishop of Blois, and for ten years (1791-1801) ruled his diocese with exemplary zeal. An ardent republican, it was he who in the first session of the National Convention (September 21, 1792) proposed the motion for the abolition of the kingship, in a speech in which occurred the memorable phrase that "kings are in the moral order what monsters are in the natural".

On November 15 he delivered a speech in which he demanded that king Louis XVI should be brought to trial, and immediately afterwards was elected president of the Convention, over which he presided in his episcopal dress. During the trial, being absent with other three colleagues on a mission for the union of Savoy to France, he along with them wrote a letter urging the condemnation of the king, but attempted to save the life of the monarch by proposing that the death penalty should be suspended.

When, on November 7, 1793, Jean-Baptiste-Joseph Gobel, bishop of Paris, was intimidated into resigning his episcopal office at the bar of the Convention, Grégoire, who was temporarily absent, hearing what had happened, faced the indignation of many deputies, refusing to give up either his religion or his office. This display of courage ultimately saved him from the guillotine.

Throughout the Reign of Terror, in spite of attacks in the Convention, in the press, and on placards posted at the street corners, he appeared in the streets in his episcopal dress and daily read mass in his house. After Maximilien Robespierre's fall (the Thermidor), he was the first to advocate the reopening of the churches (speech of December 21, 1794).

He also tried to get measures put in place for restraining the vandalism, extended his protection to several artists and writers, and devoted attention to the reorganization of the public libraries, the establishment of botanic gardens, and the improvement of technical education. In fact, he coined the term, vandalism, in a series of three monumental reports in 1794, i.e., Report on the Destruction Brought About by Vandalism,... (op. cit., J.L. Sax, p. 1149; "Vandalism", Oxford English Dictonary, 2nd ed.). He is credited by scholars (e.g. Joseph Sax) with the idea of preservation of cultural objects.