The Unidad Especial de Intervención (UEI) (English: Special Intervention Unit) is the only tier one police tactical unit of the Spanish Civil Guard (English: Civil Guard) that specialized in counterterrorism and hostage rescue crisis management, high-risk tactical special operations, quick raid to capture or kill (if necessary) high-value targets, and VIP protection.

The unit's missions primarily involve anti-irregular military, apprehension of armed and dangerous criminals, counterterrorism and hostage rescue, executive protection, high-risk tactical law enforcement situations, operating in difficult to access terrain, protecting high-level meeting areas, providing security in areas at risk of attack or terrorism, special reconnaissance in difficult to access and dangerous areas, support crowd control and riot control, and tactical special operations.

The exact scope of UEI operations and total number of personnel are not published.

In 2008, on the occasion of the Unit's 30th anniversary, its commanding officer revealed that the UEI had until then participated in 375 operations, in which 563 hostages had been freed and 640 people arrested, of whom 141 belonged to terrorist groups.

He also revealed that due to the demanding selection process, of the 26 applicants that had applied to join the Unit that year, only four had been admitted.