Arthur Henry Hallam (February 1, 1811 - September 15, 1833) was an English poet, best known as the subject of In Memoriam, a major work by his best friend, Alfred Tennyson. Hallam has been described as the jeune homme fatal of his generation.

Hallam was born in London, son of a historian, Henry Hallam. He attended school at Eton, where he met future British Prime Minister William Ewart Gladstone. The two engaged in a youthful and intense mutual infatuation, though there is no evidence of any homosexual activity. Their four year relationship ended in 1828 when Hallam left to travel in Italy and William Ewart Gladstone, to attend the University of Oxford.

In 1829, he went up to Trinity College, Cambridge, where he met Tennyson. Both joined a group known as the Cambridge Apostles. Their shared interests led to a close friendship, and Arthur became engaged to Tennyson's sister, Emilia Tennyson. While travelling abroad with his father, he died suddenly at Vienna, of a brain haemorrhage.

Hallam is the "A. H. H." of the dedication of In Memoriam and Tennyson not only dedicated one of his greatest poems to Hallam, but named his elder son after his late friend.