The Landwehr was a type of militia found in 19th- and early 20th-century Europe.

In German, the word means "defence of the country"; but the term as applied to an insurrectional militia is very ancient, and lantveri are mentioned in Baluzii Capitularia, as quoted in Hallam's Middle Ages, i. 262, 10th ed.

The landwehr in Prussia was first formed by a royal edict of 17 March 1813, which called up all men capable of bearing arms between the ages of eighteen and forty-five, and not serving in the regular army, for the defence of the country. After the peace of 1815 this force was made an integral part of the Prussian army, each brigade being composed of one line and one landwehr regiment. This, however, retarded the mobilization and diminished the value of the first line, and by the re-organization of 1859 the landwehr troops were relegated to the second line.

In Austria the landwehr was a totally different organization. It was in reality a cadre force existing alongside the regular army, and to it were handed over such recruits as, for want of vacancies, cannot be placed in the latter.

In Switzerland the landwehr is a second line force, in which all citizens serve for twelve years, after passing twelve in the Auszug or field army.