Mary, Queen of Scots, was queen regnant of Scotland and was the daughter of James V of Scotland (son of James IV and Margaret Tudor) and Mary of Guise. She had become queen when she was just six days old. The bridegroom was the son of Matthew Stuart, the 4th Earl of Lennox and Margaret Douglas (daughter of Margaret Tudor, Henry VIII's sister). Mary and Darnley were related; they were half-cousins.
The banns for the marriage had been read in St Giles's Cathedral, High Kirk of Edinburgh, on Sunday 22nd July and in that afternoon Darnley was made Duke of Albany. On Saturday 28th July, heralds proclaimed the forthcoming marriage of Mary and Darnley at the Market Cross in Edinburgh and proclaimed that Darnley would be made king following the wedding.
At 6 am on Sunday 29th July, the couple got married in Mary's private chapel at Holyrood Palace (the Palace of Holyroodhouse), Edinburgh. The bride, who had been married before, to Francis II of France, and had been widowed following his death in 1560, wore her "deuil blanc" (mourning attire) was led to the altar by the Earls of Lennox and Atholl. The couple made their vows and Darnley placed three rings on Mary's right hand. After prayers, Darnley left, leaving Mary to celebrate the nuptial mass without him. Historian John Guy writes that Darnley "wished to avoid the charge of 'idolatry'".
At midday on Monday 30th July heralds proclaimed that Darnley was King of Scotland, with the couple's official title being "Henry and Marie, King and Queen of Scotland.
The marriage was not to be happy for very long. In March 1566, Darnley, with a gang of friends, murdered Mary's private secretary, David Rizzio, in front of a pregnant Mary. Darnley was apparently jealous of Mary's friendship with Rizzio. Mary gave birth to Darnley's son, the future James VI of Scotland (James I of England) on 19th June 1566. Darnley's increasingly erratic behaviour, along with his desire to be awarded the Crown Matrimonial (the right to co-reign with Mary) had led to him becoming unpopular, and he became a real problem for Mary and the Scottish Lords. In February 1567, the problem was solved when Darnley was killed in an explosion at Kirk O'Field. It is thought that James Hepburn, Lord Bothwell, supplied the gunpowder but he was acquitted of murder in April 1567. On the 24th April 1567, Mary was kidnapped by Bothwell (it is unclear whether this was planned by Mary and Bothwell) and allegedly raped. They were married on the 15th May 1567.
The very best book there is, in my opinion, on Mary, Queen of Scots is My Heart is My Own: The Life of Mary, Queen of Scots by John Guy and we have a recording of John talking about Mary - members can click here to listen to it.