Baron Clitheroe of Downham in the County of Lancaster is a title in the Peerage of the United Kingdom. It was created in the 1955 Birthday Honours for the Conservative politician Ralph Assheton, who had previously served as Financial Secretary to the Treasury.^[3] He was the son of Ralph Cockayne Assheton, for many years a member of the Lancashire County Council, who had been created baronet of Downham in the County of Lancaster, on 4 September 1945. Three months after being raised to the peerage, Lord Clitheroe succeeded his father in the baronetcy. As of 2017^[update], the titles are held by the first Baron's son, the second Baron, who succeeded in 1984.^[2]

In the immediate aftermath of World War II, Ralph Assheton also acquired title to the manorial and mineral rights as well as land holdings within the former Honour of Clitheroe. These were purchased out of the Clitheroe Estate Company following its administration in 1945. They included the Lordship of the Forest of Pendle.

The Assheton family, also spelled Ashton, derive from Ashton-under-Lyne. The military commander Sir John de Assheton (or de Ashton) was among their ancestors.^[2]

The family seat is Downham Hall, near Downham, Lancashire.

• Sir Ralph Cockayne Assheton, 1st Baronet (1860–1955)^[2]
• Sir Ralph Assheton, 2nd Baronet (1901–1984) (created Baron Clitheroe in 1955)