NRP Almirante Gago Coutinho (A523) is a ship of the Portuguese Navy' Dom Carlos I-class survey vessels (ex-US Stalwart-class ocean surveillance ship adapted in Portugal for the execution of hydrography and oceanography surveys).

The Stalwart-class ocean surveillance ships were succeeded by the longer Victorious class.

[1] USNS Assurance was a Stalwart-class modified tactical auxiliary general ocean surveillance ship of the United States Navy.

Stalwart-class ships were originally designed to collect underwater acoustical data in support of Cold War anti-submarine warfare operations in the 1980s.

In 1999, ex-USNS Assurance was transferred to Portugal and is now NRP Almirante Gago Coutinho survey ship.