Nicolas "Nic" Mosar (25 November 1927 – 6 January 2004) was a Luxembourgish politician, jurist, and diplomat.

A Christian Social People's Party (CSV) member, Mosar was elected to the communal council of Luxembourg City in 1959, and sat in the council until 1984, including a period as an échevin.

Leaving domestic politics, Mosar replaced Gaston Thorn as Luxembourg's European Commissioner in 1985, taking on the brief of European Commissioner for Energy.

After four years in the job, he moved to bilateral diplomacy, becoming Luxembourg's Ambassador to Italy (1989–1992).

His son, Laurent, now sits in the Chamber of Deputies and Luxembourg City council for the CSV, just as Nicolas had.