Palaiseau is a commune with 30,316 inhabitants (as of January 1, 2011 ) and the sub-prefecture ( sous- préfecture ) of the eponymous arrondissement in the department of Essonne, south of Paris adjacent. Through the city flows the Yvette.

The place belongs to the immediate south-western catchment area of the capital, a preferred residential area and home to two elite high schools ( Grandes écoles ), the École Polytechnique and the Ecole Nationale des Ponts et Chaussées. With the company " SOLEMS " here also a growth-oriented high- tech engineering has settled, which specializes mainly on solar cells and thin film modules made of amorphous silicon, as well as light sensors and photovoltaic stand-alone systems.

The Westphalian Unna is the German twin town of Palaiseau.