This article is about the particular significance of the year 2003 to Wales and its people.
- February - Former Conservative Assembly leader Rod Richards is declared bankrupt with debts estimated at over £300,000.
- 27 February - Rowan Williams is enthroned as Archbishop of Canterbury. Dominic Walker is installed as his replacement as Bishop of Monmouth
- 9 March - Ron Davies announces that he is leaving politics after being asked to stand down by his local party following further revelations by the press about his private life.
- 29 March - Porthmadog Cob is bought by the Welsh Assembly Government and the road toll is discontinued after 192 years .
- 1 May - In the National Assembly for Wales election, Labour win 30 seats, enabling them to form a government. Following disappointing results for Plaid Cymru, Ieuan Wyn Jones stands down as party president and leader of the assembly group.
- 19 June - Prince William of Wales visits Bangor and Anglesey, to mark his 21st birthday (on 21 June).
- October - Dafydd Iwan, newly elected President of Plaid Cymru, escapes a driving ban for speeding offences on the grounds that he needs to drive to fulfil his musical and political engagements.
- 12 October - The Friends of the Leinster hold a service at Holyhead to commemorate the 85th anniversary of the sinking of RMS Leinster by a German U-boat.
- November - Michael Howard becomes leader of the Conservative Party.
- December - Dafydd Wigley is appointed Pro-Chancellor of the University of Wales.
- 7 December - The Wales & Borders train operating franchise is awarded for a 15-year period to Arriva Trains Wales.
- North Hoyle Offshore Wind Farm commences operation.
- The former Brains Brewery site in Cardiff is redeveloped into the 85,000 sq ft (7,900 m2) "Old Brewery Quarter".
- Veteran Cardiff politician Stefan Terlezki goes to the European Parliament to press the case for eventual Ukrainian membership of the European Union.
- In Channel 4's 100 Worst Britons poll (which includes only living people), the following entries have Welsh connections:
Arts and literature
- 5 January – Roy Jenkins, politician and Chancellor of Oxford University, 82
- 6 January – Glyn Davies, economist, 83
- 17 January – Goronwy Daniel, academic and civil servant, 88
- 26 January - Kingsley Jones, rugby union prop, 67
- 3 February – Trevor Morris, football player and manager, 82
- 26 February – Brian Evans, footballer, 60
- 14 April - Bob Evans, rugby player, 82
- 13 May – John Savage, prime minister of Nova Scotia 1993-97, 70
- 29 May – Trevor Ford, footballer, 79
- 8 June – Leighton Rees, darts player, 63
- 10 June – Phil Williams, politician, 64
- 16 June - Ivor Bennett, rugby player, 90
- 17 July – Dr David Kelly, government weapons expert, presumed suicide, 59
- 21 July – John Davies, Olympic athlete of Welsh descent, 65
- 3 August - Norah Isaac, educationalist
- 5 August – Benjamin Noel Young Vaughan, Bishop of Swansea and Brecon, 85
- 20 September – Gareth Williams, Baron Williams of Mostyn, politician, 62
- 25 September
- 29 September – Billy Cleaver, Wales international rugby union player and colliery manager, 82
- 7 October – Henry Herbert, 17th Earl of Pembroke, 64
- 23 November – Paul Grant, bodybuilding champion, 60
- 27 November – Dai Francis, singer, 73
- 1 December – Hugh Rees, politician, 75
- 19 December – Roy Hughes, Baron Islwyn, politician, 78
- 20 December – Robin Williams, broadcaster and essayist, 80
- date unknown – Brian Morgan Edwards, businessman