01Short answer
Mamdani was born in Uganda. He moved to New York City as a child and became a naturalised American citizen in 2018.
As mayor, his legal and political office is American and local: Mayor of New York City. The biography still matters because his campaign often spoke about immigration, belonging and public life.
For most public purposes, the clean answer is: born in Uganda, raised in New York, naturalised in the United States.
02Why it matters
The country question often sits behind arguments about legitimacy. The relevant public facts are citizenship, election, oath of office and the power of the office he holds.
Birthplace can explain biography. It does not reduce the mayoral record. The record is made through housing, transit, public safety, budget and federal pressure.
03Where to go next
For the legal question about national office, use the Mamdani for President page. For city power, use the delivery record and policy pages.