St Andrew's Cathedral (Scottish Gaelic: Cathair-eaglais Naomh Anndra), or the Cathedral Church of Saint Andrew, is a cathedral of the Scottish Episcopal Church situated in the Scottish city of Aberdeen. It is the see of the Bishop of Aberdeen and Orkney, who is the Ordinary of the Diocese of Aberdeen and Orkney.

It is a Category A listed building.

The church opened in 1817 as St Andrew's Chapel and was raised to cathedral status in 1914. The original building was designed in the perpendicular Gothic style by architect Archibald Simpson, one of Simpson's many commissions in the city. While three sides of the cathedral were built out of the local granite, for which Aberdeen is famous, the facade of the structure, facing King Street, Aberdeen, was built from sandstone for economical reasons despite Simpson's opposition. The cathedral comprised nave and flanking aisles with sandstone ashlar to the King Street elevation and snecked granite rubble to the rear. The chancel was added by George Edmund Street, 1880 and the porch by Robert Lorimer in 1911.

Aberdeen is where the first bishop of the Episcopal Church in the United States of America, Samuel Seabury was ordained in 1784. Seabury was consecrated bishop by Robert Kilgour, Bishop of Aberdeen and Primus of Scotland; Arthur Petrie, Bishop of Ross and Moray; and John Skinner, coadjutor bishop of Aberdeen. The consecration took place in "an upper room" of the house of Skinner, then leader of the St Andrew's congregation, approximately 500 metres from the present cathedral. The approximate site of the house is marked by a polished granite tablet on the wall of Marischal College.

During the 1930s, the cathedral was renovated to commemorate the 150th anniversary of Seabury's consecration. There had been a plan to build an elaborate, cruciform cathedral with central tower, commemorating Bishop Seabury's consecration on the site currently occupied by Aberdeen City Council's headquarters. This was to have been a gift of the Episcopal Church in the United States of America, however, the Wall Street Crash halted this plan. Instead, the existing church was enlarged and embellished by Ninian Comper. In 1938, the US ambassador Joseph Kennedy, accompanied by his 21-year-old son John F. Kennedy, opened an extension. Comper's decorative scheme is largely intact; it includes a vaulted ceiling with decorative panels depicting the arms of the then 48 US states and local families. The chancel has a large gold-painted baldachino and carved oak screen.

Until the late 1970s and early 1980s, the cathedral was Anglo-Catholic in tradition. In 1982, the cathedral provost, Donald Howard, declared in a sermon the cathedral would remove the large crucifix and four of the six candles on the high altar for Lent so that the altar could be free-standing to permit a 'westward' celebration of the Eucharist, celebrant facing the congregation rather than back to the people. Worship has since become more "broad" in nature, whilst retaining the dignity of cathedral worship.

In April 2020, church officials said that financial difficulties could mean that the cathedral might not re-open after the COVID-19 pandemic. In June 2020, Bishop Anne Dyer and the Cathedral Trustees and Chapter announced that the cathedral would close temporarily from September 2020, because of problems with the fabric of the building. The congregation continued to gather for worship online.

The cathedral reopened for worship on Sunday, 5 December 2021, with an inaugural service of Advent Carols. The congregation continues to gather for worship on Sundays at 10.45am and on Thursdays at 10am.

The cathedral, which has a splendid acoustic, houses one of the finest three manual pipe organs in Scotland. The organ by Bruce of Edinburgh (1818) was rebuilt and enlarged by Hill, Norman & Beard. The cathedral has been served by a number of distinguished organists and masters of the choristers including:

• George Trash
• John Cullen
• Richard Galloway
• Frederick ("Bill") Fea
• David McGinnigle
• Geoffrey Pearce 1978 – 1983 (afterwards organist of Bridlington Priory) and Selby Abbey
• Professor Andrew Morrisson 1983 – 2020
• Christopher Cromar 2020–2021

• Revd Canon Captain Gerry Bowyer
• Revd Canon Neil Brice
• Revd Canon Vittoria Hancock
• Revd Canon Jeremy Paisey
• Revd Canon John Walker

• Religion in Scotland
• St Machar's Cathedral — the original cathedral in Aberdeen, now a High Kirk of the Church of Scotland
• St Mary's Cathedral — cathedral of the Roman Catholic Diocese of Aberdeen

57°08′57″N 2°05′35″W / 57.1491°N 2.0931°W / 57.1491; -2.0931