Paul Kenneth Baillie Reynolds, CBE (1896–1973) was a British classical scholar and archaeologist who studied specialised Roman troops such as the frumentarii and the vigiles.

He was the son of Louis Baillie Reynolds, a stockbroker, and novelist Gertrude Minnie Robins. He studied at Hertford College, Oxford between 1915–1919, his studies being interrupted by World War I. He served in the Royal Artillery.

By 1921, he had become a Pelham student at the British School in Rome. While Rome he wrote books and articles for which he is well remembered (e.g., The Troops Quartered in the Castra Peregrina JRS 13 1923, pages 168–87; The Vigiles of Imperial Rome, Oxford 1926). Baillie Reynolds extensively researched the remains of ancient Rome's aqueducts. He stayed at Rome until 1923.

In 1924, Baillie Reynolds became a lecturer on Ancient history at Aberystwyth University. While at Aberystwyth, he also directed the excavations of Kanovium, the Roman fort at Caerhun, North Wales, over a period of four summers from 1926. He published a series of reports on these excavations in Archaeologia Cambrensis, which were published as a collection in 1938; they are considered a classic study of their type. At this time he also published numerous books and reports on archaeological sites in Britain and beyond. He is best known for his book, "The Vigiles of Imperial Rome" (1926). In 1934 he became an Inspector of Ancient Monuments, England, and Chief Inspector from 1954 to 1961. As an Inspector, he wrote guide books for some of the many sites under Government care, some of which remained in print for over twenty years (e.g., "Chysauster" Cornwall, HMSO Guides, London 1960).

His last significant task was to oversee repairs to the Aqua Claudia aqueduct in Rome, which ran through the grounds of the British Embassy. A report of this work was published in the journal Archaeologia Volume 100, 1966. It was his last publication, and he died in 1973.

Baillie Reynolds had a distinguished career, recognised by his honours, firstly becoming an Officer of the Order of the British Empire and subsequently made a Commander of the Order.

During World War II, Baillie-Reynolds was one of the founding members of the Monuments Men (M.F.A.A.), who sought to protect European art treasures during and after the war.