In physics, the weber (symbol: Wb) is the SI derived unit of magnetic flux. It is named after the German physicist Wilhelm Eduard Weber (1804 - 1891).

The weber may be defined in terms of Faraday's law, which relates a changing magnetic flux through a loop to the electric field around the loop. A change in flux of one weber per second will induce an emf of one volt.

In SI base units, the dimensions of the weber are kg·m²·s^-2·A^-1. In derived units, they are volt-seconds (V·s).

The weber is a large unit, equal to 10⁸ maxwells. Magnetic flux on the order of magnitude of a weber is rarely observed.