Battle of Bryn Glas: Glyndŵr's Welsh army defeat the English on the England/Wales border; Edmund Mortimer, son of the 3rd Earl, is taken and defects to the Welsh cause.
September – the English Parliament passes penal Laws against Wales which stop the Welsh from gathering together, obtaining office, carrying arms and living in English towns. Any Englishman who marries a Welsh woman also comes under the laws.
21 July – Battle of Shrewsbury: Henry IV defeats a rebel army led by "Hotspur" Percy who has allied with the Welsh prince Owain Glyndŵr. Percy is killed in the battle by an arrow in his face.
August – William du Chastel leads a French raid on Plymouth which causes substantial damage.
14 January – the fourth Parliament of King Henry IV opens for a session of two months. Henry grants it the power to appoint Royal Councillors and hold them to account for expenditure.
20 March – as the English Parliament adjourns, Henry IV gives royal assent to acts that have passed, including the Gold and Silver ("Multipliers") Act, intended to prohibit alchemists from performing transmutation of common substances into precious metals.
14 June – Welsh rebel leader Owain Glyndŵr allies with France against the English. He has begun to hold parliamentary assemblies (first on 10 May at Dolgellau) and on 21 June is formally crowned Prince of Wales at Harlech.
16 October – the 5th Parliament of Henry IV (summoned 25 August), nicknamed "The Unlearned Parliament" because Henry refuses to allow lawyers to sit, opens for a 4-week session in Coventry, closing on 13 November. Henry withdraws its powers of oversight over the Royal Council.
1405
11 March – Battle of Grosmont (Monmouthshire): English defeat Welsh rebels.
8 June – following the collapse of their revolt, Richard Scrope together with Thomas de Mowbray, 4th Earl of Norfolk, and Scrope's nephew, Sir William Plumpton, are tried by a special commission and beheaded at York. Scrope is the first English prelate to suffer judicial execution.
August – Welsh rebels, assisted by the French, unsuccessfully attack Worcester.
1 March – Parliament meets, and continues to sit until December, when it finally achieves its aims of nominating and ensuring the payment of members of the Royal Council.
30 March – the heir to the Scottish throne, Prince James, having been captured by English pirates on 22 March, is detained in England. On 4 April he becomes King James I of Scotland on the death of his father but remains detained in England for 18 years.
19 February – Battle of Bramham Moor: Thomas de Rokeby, Sheriff of Yorkshire, suppresses the Percy rebellion in the north, Percy and Bardolf both being killed.
September – Henry, Prince of Wales, retakes Aberystwyth from Owain Glyndŵr.
Glass painter John Thornton of Coventry completes the largest medieval window in England, at York Minster.
1409
January – the Welsh surrender Harlech Castle to the English.