In general, official recognition of foreign university degrees equivalent to Spanish Bachelor's, Master's or Doctorate degrees are required in order to apply for some positions at institutions or to incorporate to the Spanish system.
A description of the procedure for recognition or equivalence of a foreign university qualification is described here.
The equivalence of foreign higher education degree at the academic level of official university degree or master's degree dependes on the Ministry of Science, Innovation and Universities.
The procedure is online and starts with the registration in the Electronic Office. The application is permanently open and it requires the payment of a fee. All the information can be found here.
⚠️ Take into account that there exists a similar procedure called "Homologación", which aims to recognize foreign degrees for regularized professional activities like engineer, medical doctor or shool teacher (more information here).
The Spanish universities are responsible for the procedure of equivalence of foreign doctoral degrees. The procedure starts with the application of the interested party, who should go to the rectorate of the corresponding university.
Here we list the links to the procedures of some universities: