Sint-Gillis-Waas (; ) is a municipality located in the Belgian province of East Flanders. The municipality comprises the towns of De Klinge, , Sint-Gillis-Waas proper and . On 1 January 2018, Sint-Gillis-Waas had a total population of 19,273. The total area is 54.98 km<sup>2</sup> which gives a population density of 357 inhabitants per km<sup>2</sup>.