Johannes Letzner (29 November 1531 – 16 February 1613) was a Renaissance-era German Protestant priest and historian of Lower Saxony, in particular of Brunswick-Lüneburg.
Letzner studied briefly at Wittenberg University in 1550–1551 before moving to Uslar as cantor and school master, and later as vicar to Parensen (1553) Langenholtensen (1564), Lüthorst (1583), Iber (1589) and finally to Strodthagen where he retired in 1610 and died three years later.
His magnum opus was going to be a "Great Chronicle of Brunswick-Lüneburg" ("Große Braunschweig-Lüneburg-Göttingensche Chronika") in eight volumes, on which he worked during 36 years of his life.
Conradus Fontanus is one of the purported sources used by Letzner, allegedly a medieval chronicler with a floruit close to 1200.
Fontanus was included by Adelung in his continuation of Jöcher's Gelehrten-Lexicon, but in 20th century scholarship has come to be considered as of dubious historicity, or spurious.