Seneffe is a Walloon municipality located in the Belgian province of Hainaut. On January 1, 2006 Seneffe had a total population of 10,743. The total area is 62.77 km² which gives a population density of 171 inhabitants per km².

The Castle of Seneffe, now a museum belonging to the French Community of Belgium, is located in the municipality.

Between 1965 and 1982 Seneffe was the location of a car plant belonging to British Leyland, which in its later years assembled models including the Mini and the Austin Allegro from crated kits shipped from the company's Cowley facility. A significant milestone was reached in June 1977 when the plant produced its 500,000th vehicle, an Austin Allegro 1300 Special. The Seneffe plant was closed in 1982 as the company's aging model range lost market share across Europe, with further loss of demand resulting from the depressed state of the UK economy at the time. With alternative employment opportunities limited, the plant closure triggered considerable bitterness locally.