The Comunidade Intermunicipal da Lezíria do Tejo (European Portuguese pronunciation: [lɨˈziɾiɐ ðu ˈtɛʒu]; "Tagus Floodplain") is an administrative division in Portugal. It was established as an Associação de Municípios in 1987, converted into a Comunidade Urbana in 2003, and converted into a Comunidade Intermunicipal in November 2008. It is also a NUTS3 subregion of the Oeste e Vale do Tejo. The seat of the intermunicipal community is the city of Santarém. Lezíria do Tejo comprises municipalities of the former districts of Santarém and Lisbon. The population in 2011 was 247,453, in an area of 4,275 square kilometres (1,651 sq mi). In the past, the territory of this administrative division was roughly entirely set in the historic province of Ribatejo and had nothing to do with the historic province of Alentejo. Lezíria is the Portuguese word (from the Arabic الجزيرة, al-jazira, "the island") for floodplain or freshwater marsh. Tejo is the name of the main river in the region. The Lezíria is a well-renowned center of intensive farming, horse breeding and animal husbandry.

It is composed of 11 municipalities:

Municipality	Population (2011)	Area (km)
Almeirim	23,376	222.12
Alpiarça	7,702	95.36
Azambuja	21,814	262.66
Benavente	29,019	521.38
Cartaxo	24,462	158.17
Chamusca	10,120	746.01
Coruche	19,944	1115.72
Golegã	5,913	84.32
Rio Maior	21,192	272.76
Salvaterra de Magos	22,159	243.93
Santarém	61,752	552.54
Total	247,453	4,274.98

• Companhia das Lezírias
• Lezíria Bridge
• Ribatejo

• Official website CIM Lezíria do Tejo