The Longos mansion (Greek: Μέγαρο Λόγγου), also known as the Red house (Κόκκινο Σπίτι) due to its red brick exterior, is a three-storey house in Agias Sofias Square in the center of Thessaloniki. It was designed in 1926 by architect for the family of Grigorios Longos, a wealthy textile industrialist from Naousa, in the Neobyzantine style. He later gave it to his brother, Ioannis, which is why it is known as "Ioannis Longos mansion". In 1983, it was listed by the Greek Ministry of Culture for preservation.