NNL may refer to: Narnaul railway station — a railway station in Haryana, India National Natural Landmark — a natural history conservation program of the U.S. Secretary of the Interior National Nuclear Laboratory — the UK's government-owned commercially operated fully customer-funded nuclear technology service provider Nigeria National League, football league Negro National League (1920–1931) — one of the several Negro leagues which were established during the period in the United States in which organized baseball was segregated Negro National League (1933–1948) — established two years after the first Negro National League had disbanded Noether normalization lemma — a theorem in commutative algebra No net loss – an environmental policy approach