| Image Map1: | LocatieWestland.png |
| De Lier | |
| Subdivision Type: | Country |
| Subdivision Name: | Netherlands |
| Subdivision Type1: | Province |
| Subdivision Name1: | South Holland |
| Subdivision Type2: | Municipality |
| Subdivision Name2: | Westland |
| Coordinates: | 51.9736°N 4.25°W |
| Area Total Km2: | 8.92 |
| Population: | 11.925 |
| Postal Code: | 2678 |
| Website: | http://www.gemeentewestland.nl |
| Blank Name Sec1: | Transport |
| Blank1 Name Sec1: | Major roads |
| Blank1 Info Sec1: | N223 |
De Lier (in Dutch; Flemish pronounced as /də ˈliːr/) is a village in the Dutch province of South Holland. It is a part of the municipality of Westland.
De Lier lies about 5 km north of Maassluis, and is about 6feet below sea level. The village got its name from the name of an old river called .
De Lier used to be a separate municipality. On 26 March 1963, it was granted its own coat of arms, and on 14 April 1965, it adopted the flag it has today. On 1 January 2004, it merged with Naaldwijk, 's-Gravenzande, Monster, and Wateringen to form the municipality of Westland. The former municipality covered an area of 8.93 square kilometres.
In 2001, De Lier had 9415 inhabitants. In 2003, De Lier had 11,400 inhabitants. The built-up area of the village was 2.2 km², and contained 3494 residences.[1] The statistical area "De Lier", which can also include the peripheral parts of the village as well as the surrounding countryside, has a population of around 11,470.[2]