Adam of Usk (Welsh: Adda o Frynbuga, c. 1352 – 1430) was a Welsh priest, canonist, and late medieval historian and chronicler.
Born at Usk in what is now Monmouthshire (Syr Fynwy), south-east Wales, Adam received the patronage of Edmund Mortimer, 3rd Earl of March, who inherited the Lordship of Usk (Brynbuga) through his wife Philippa. Mortimer encouraged and enabled Adam to eventually study at Oxford, where he obtained his doctorate and became extraordinarius in Canon law.
Adam settled at Oxford University as a teacher of law. Here by his own admission he was involved in armed struggle in 1388 and 1389 between the Northerners and the Southerners, which included the Welsh.
Adam left Oxford and practised his profession for seven years as an advocate in the archiepiscopal court of Canterbury, 1390–1397, sitting on the Parliament of 1397. In 1399 he accompanied the Archbishop and Bolingbroke's army on the march from Bristol to Chester. These experiences and the connection with Thomas Arundel shaped his views thereafter. He was hostile in his chronicle to Richard II, was a member of the commission appointed to find secure legal grounds for his deposition, and met with the King during his captivity in the Tower of London.
Adam was rewarded for his part in Richard II's surrender, imprisonment and fall by being granted the living of Kemsing and Seal, and later made a prebend in the church of Bangor. These nicely supplemented his professional legal income and status. However one living, his title to the prebend of Llandygwydd in Cardiganshire given under the college of Abergwili, was contested by one Walter Jakes, alias Ampney, who had obtained it by exchange in 1399. The two were in an affray, in Westminster, in November 1400, which resulted in charges being brought against Adam and his company for highway robbery. The outcome is unknown, however it did not immediately limit his legal activities, as he continued as a lawyer.