The amino acid lysine is among the world’s most important biotechnological products, and enabling its manufacture from the most attractive new materials is an ever-present challenge. In this study, we describe a cell factory of Corynebacterium glutamicum, which produces lysine from mannitol. A preliminary mutant obtained by the deletion of the mannitol repressor MtlR in the glucose-based, lysine-producing C. glutamicum produced only small amounts of lysine. This limitation was due to the significant accumulation of fructose and a limited NADPH supply, which caused a low flux of only 6% into the oxidative pentose phosphate (PP) pathway. Subsequent expression of fructokinase slightly increased production but failed to substantially redirect the flux from the Emden-Meyerhof-Parnas (EMP) pathway to the PP pathway. This suggested the design C. glutamicum SEA-3, which overexpressed the NADPH-dependent glyceraldehyde 3-phosphate dehydrogenase GapN from Streptococcus mutans and coupled the EMP pathway flux to NADPH formation. When grown on mannitol, the SEA-3 strain had a lysine yield of 0.24 mol mol-1 and a specific productivity of 1.1 mmol g-1 h-1, approximately 50% and 70% higher, respectively, than those of the basic producer. A computational pathway analysis revealed that this design would potentially enable a lysine yield of 0.9 mol mol-1, providing room for further development. Our findings open new avenues for lysine production from marine macroalgae, which is farmed globally as an attractive third-generation renewable resource. Mannitol is a major constituent of these algae (up to 30% and higher) and can be easily extracted from their biomass with hot water.