Técnicas Reunidas, S. A. (IBEXC: TRE) is a Spanish multinational company specialized in engineering and construction of infrastructure for the oil and gas sector. The company is listed on the Spanish Continuous Market and until June 2019 was part of the IBEX 35.

Técnicas Reunidas' activity can be divided into four large areas: refining and petrochemicals; production and natural gas; energy; and infrastructure. As a complement to these areas, it is also dedicated to the development of advanced technologies and patents for different industrial processes.

The history of Técnicas Reunidas dates back to 1959, when as a result of the association between several Spanish businessmen and the North American engineering company The Lummus Company, Lummus Española, S.A. was created.

In 1963, Técnicas Reunidas built its first complete refinery in Spain, thus beginning its career as a specialist in refining units.

In 1968, he built the Luján de Cuyo refinery (Argentina) for Yacimientos Petrolófilos Fiscales, SA, being his first project abroad.

In 1972 the company absorbed Tecniresa, adopting the current corporate name and becoming a Spanish private capital company.

Starting in the 1980s, under the direction of Álvaro García-Agulló Lladó and presidency of José Lladó Fernández-Urrutia, there has been a great international expansion, and currently, it develops most of its activity outside of Spain, mainly in the countries of the Middle East, Latin America, the Far East and the Mediterranean area (mainly North Africa and Turkey).

In 2022, during the COVID-19 pandemic, the Government of Spain, through the State Society of Industrial Participations (SEPI), granted the company aid of 340 million euros.[2]​ The company began to repay the loan in February 2024.[3]​.