Duncan McNeill, 1st Baron Colonsay FRSE was a Scottish advocate, judge and Tory politician. He was Lord Justice General and Lord President of the Court of Session between 1852 and 1867.

The Lord President of the Court of Session and Lord Justice General is the most senior judge in Scotland, the head of the judiciary, and the presiding judge of the College of Justice, the Court of Session, and the High Court of Justiciary. The Lord President holds the title of Lord Justice General of Scotland and the head of the High Court of Justiciary ex officio, as the two offices were combined in 1836. The Lord President has authority over any court established under Scots law, except for the Supreme Court of the United Kingdom and the Court of the Lord Lyon.