GHαFaS is a new Fabry-Perot system available at the William Herschel Telescope. It was mounted, for the first time, at the Nasmyth focus of the 4.2 m WHT in La Palma in 2007 July. With a spectral resolution of the order R~15000 and a seeing limited spatial resolution, GHαFaS provides a new look at the Hα-emitting gas over a 4 arcminutes circular field in the nearby universe. Many types of objects can be observed with a scanning Fabry-Perot system on a 4.2 m class telescope such as galaxies, HII regions, planetary nebulae, supernova remnants outflows from stars and the diffuse interstellar medium. Astronomers from the Laboratoire d'Astrophysique Experimentale (LAE) in Montreal, the Laboratoire d'Astrophysique de Marseille (LAM), and the Instituto de Astrofisica de Canarias (IAC), have inaugurated GHαFaS by studying in detail the dynamics of nearby spiral galaxies. A robust set of tools for reducing and analyzing the data cubes obtained with GHαFaS has also been developed.