WEAVE is a new multi-object spectrograph planned for the 4.2m William Herschell Telescope (WHT) located in the Observatorio del Roque de los Muchachos, on La Palma island. This instrument combines large field of view (2 degree diameter field) and large spectral capability. In particular, WEAVE will allow the users to obtain up to 1000 spectra of astronomical objects in a single exposure. The instrument will also have a multi-integral-field-unit (IFU), which will be useful for integral field spectroscopy of galaxies. The instrument will offer and spectral resolution of R=5000 over wavelength range 370-950 nm and a higher resolution mode at R=20000 over two more limited wavelength regions: 410-460 nm and 600-678 nm. This instrument will be crucial for the near future of the telescope. WEAVE will not only renew the instrumentation at the WHT but place this telescope at the top of the 4m class telescopes in the word conducting multi-object optical spectroscopic surveys. Spectrographs will be placed at the Nasmyth focus (GHRIL Laboratory), and fiber bundles will be installed at the prime focus.

During a period of five years WEAVE will produce about 15 millions spectra of various astronomical objects. With them we'll provide unique and cutting-edge science in key fields of astronomy such as the study of the Milky Way, evolution of galaxies or cosmology. In addition, this data will complement other key European projects such as GAIA and LOFAR.

This instrument is beeing disigned and developed by a consortium of institutes from Great Britain, The Netherlands, France, Italy, Mexico and Spain.