The Macedonian Scientific Institute (MSI, Bulgarian: Македонски научен институт) is a Bulgarian scientific organisation, which studies the Region of Macedonia and mostly the Macedonian Bulgarians.
It was founded in 1923 from Sofia University professors and scholars, among the Macedonian Bulgarians. In the beginning the Institute began to publish the journal "Macedonian Review" and other scientific studies on the Bulgarian population in Macedonia. The "Macedonian Review" was concerned with Macedonia and all branches of the study of its history, culture and social life. In the 1930s the Macedonian Scientific Institute was managed by the known Bulgarian Professor Lyubomir Miletich. Under his direction the Macedonian House of Culture in Sofia was built, where ethnographic museum and library were established. After 1945 the activity of the MSI was changed to serve the macedonistic policy on the Macedonian Question in the People's Republic of Bulgaria and the Socialist Federal Republic of Yugoslavia. The new authorities began a policy of removing of any Bulgarian influence, making Macedonia connecting link for the establishment of new Balkan Federative Republic and creating there a distinct Slav Macedonian consciousness. In 1947 the Bulgarian Communist regime "recommended" the liquidation of the MSI. The archives and the whole museum collection including the remains of the revolutionary Gotse Delchev were transported in the new established People's Republic of Macedonia.