Marc René, marquis de Montalembert (16 July 1714 – 29 March 1800) was a French military engineer and writer, known for his work on fortifications.

The intricacies of trace by which Vauban and Cormontaigne sought to minimize the power of the attack, are abandoned in favour of a simple tenaille plan so arranged that the defenders can bring an overwhelming fire to bear on the works of the besieger.

[1] Montalembert, who himself drew his idea from the practice of Swedish and Prussian engineers, furnished the German constructors of the early 19th century with the means of designing entrenched camps suitable to modern conditions of warfare.

In his own country the caste-spirit of the engineer corps was roused to defend Vauban, and though Montalembert was allowed to construct some successful works at Île-d'Aix and Oleron, he was forbidden to publish his method, and given but little opportunity for actual building.

[1] At the time of the Revolution he surrendered a pension, which had been granted him for the loss of an eye, although he was deeply in debt, particularly on account of his Ruelle foundry, on which 6000 livres were due to him from the state, which he never received.

It was the inability of his contemporaries to see that Vauban's strength lay in his parallels and batteries and not in his bastions that vitiated their methods, and it was Montalembert's appreciation of this fact which made him the father of modern fortification.