Kralj Petar Krešimir IV (pennant number RTOP-11) is a Kralj-class missile boat in service with the Croatian Navy.

Although Kralj Petar Krešimir IV was plagued with engine malfunctions and other equipment problems throughout its service life, it continues to serve with the Flotilla of the Croatian Navy along with four other missile boats.

Kralj Petar Krešimir IV was laid down in 1991 in the Kraljevica Shipyard as the first ship of the new Kobra-class missile boats that were planned for the Yugoslav Navy (JRM).

The ship was to be named after Sergej Mašera (pennant number RTOP-501) who prevented the destroyer Zagreb from falling into Italian hands during the Invasion of Yugoslavia.

[11] The next live firings didn't happen until 2015 when a single missile was launched from a coastal launcher and another one from Petar Krešimir IV's sister ship, Kralj Dmitar Zvonimir.

[12] The ship's engines proved to be problematic since it was commissioned; because they were designed for providing high speed bursts during a short period of time, they're not suited for longer patrols at lower speeds, have a high fuel consumption and have been partially operational for most of the time; problems that would plague Kralj Petar Krešimir IV throughout its service life.

Dugoročni plan razvoja Oružanih snaga Republike Hrvatske 2006–2015) in which it was stated that one of the Navy's priorities was equipping Kralj Petar Krešimir IV with new engines and anti-aircraft systems.

Although the MoD declined to comment on the potential sale to Georgia, they did confirm that they would consider offers if any were given, as well as that the ship would remain in service until a deal was made.

[20] A report about the state of the armed forces in 2011 stressed out the inoperability of the engines on Petar Krešimir IV as the single biggest maintenance problem for the Navy.

[23] Kralj Petar Krešimir IV was featured in a series of postage stamps issued by the Hrvatska pošta named "Hrvatsko brodovlje" (en.