The Glasgow Cathcart by-election to the Scottish Parliament was held on 29 September 2005. It was caused by the resignation from the Scottish Parliament of Mike Watson, who won the seat at both the 1999 and 2003 elections.
On 15 November 2004, Watson had been charged with two counts of fire-raising while attending a private reception at Edinburgh's Prestonfield House Hotel three days previously. After initially registering not guilty pleas to both charges on 23 August 2005, on 1 September he changed his plea on the first count to guilty, and had a not guilty plea accepted on the second charge. Sentencing has been deferred till 22 September. On the same day Watson admitted his guilt, he resigned from the Scottish Parliament necessitating the by-election.
The short time span between Watson's resignation and the by-election has been the cause of some controversy. George Reid, the Parliament's Presiding Officer set the date citing that it was in the best interests of the public to have it on this date, the date already set for the Livingston by-election caused by the death of Robin Cook as having alternative dates would have led to months of electioneering, which he felt was against the public interest. The Scottish National Party (SNP) leader, Alex Salmond felt that the Labour Party had brought undue pressure to bear on the Presiding Officer though and angrily charged that the date was set merely to suit Labour's purposes as they were worried about a strong SNP challenge (the SNP had come second in the constituency in recent elections).