Per Ditlev-Simonsen (born 12 June 1932) is a Norwegian politician. He was the mayor of Oslo, representing the Conservative Party, from 1995 to 2007. He stepped down on 23 August 2007 following the Swiss bank-account scandal.
Ditlev-Simonsen was an officer of the The Norwegian Royal Guards, and he later attended Stanford University getting a Master of Arts degree. After college, Ditlev-Simonsen became a partner in his father's shipping company Sverre Ditlev-Simonsen & Co (SDS) in 1955. He was a partner in the company until 1995.
The revelation caused several opposition politicians to call for Ditlev-Simonsen's resignation. Erna Solberg, the head of the Conservative Party, asked that Ditlev-Simonsen refrain from active campaigning for his party ahead of the local elections scheduled for 10 September. Even if he had not resigned, the 75 year old Ditlev-Simonsen was set to retire after the election. The incident was believed to be a cause of the Conservative's 4 percent drop in opinion polls, three weeks ahead of the election.