| John III | |
| Reign: | 1343–1356 |
| Pre-Type: | Predecessor |
| Suc-Type: | Successor |
| House: | Ascania |
| Mother: | Beata of Schwerin |
| Birth Date: | mid-1330s |
| Death Date: | 1356 |
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.
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