John III of Saxe-Lauenburg (mid 1330s – 1356) was the eldest son of Duke Albert IV of Saxe-Lauenburg and Beata of Schwerin (*?–before 1341*), daughter of Gunzelin VI, Count of Schwerin.
John III succeeded his father in 1343 as Duke of Saxe-Bergedorf-Mölln, a branch duchy of Saxe-Lauenburg.
He died without an heir and was succeeded by his younger brother Albert V. This article related to German royalty (1871–1919) is a stub.
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