Il numero romano MCMLXXX nel sistema decimale vale: 1980.
MCMLXXX in latino si scrive mille nongenti octoginta,
mentre in italiano millenovecentottanta.
MCMLXI, MCMLXII, MCMLXIII, MCMLXIV, MCMLXV, MCMLXVI, MCMLXVII, MCMLXVIII, MCMLXIX, MCMLXX, MCMLXXI, MCMLXXII, MCMLXXIII, MCMLXXIV, MCMLXXV, MCMLXXVI, MCMLXXVII, MCMLXXVIII, MCMLXXIX, MCMLXXXI, MCMLXXXII, MCMLXXXIII, MCMLXXXIV, MCMLXXXV, MCMLXXXVI, MCMLXXXVII, MCMLXXXVIII, MCMLXXXIX, MCMXC, MCMXCI, MCMXCII, MCMXCIII, MCMXCIV, MCMXCV, MCMXCVI, MCMXCVII, MCMXCVIII, MCMXCIX