Operation Ocean Shield was NATO's anti-Piracy in Somalia initiative in the Indian Ocean, Guardafui Channel, Gulf of Aden and Arabian Sea. It follows the earlier Operation Allied Protector. Naval operations began on 17 August 2009 after being approved by the North Atlantic Council, and were terminated on 15 December 2016 by NATO. Operation Ocean Shield focused on protecting the ships of Operation Allied Provider [de; no; ru; uk], which transported relief supplies as part of the World Food Programme's mission in the region. The initiative also helped strengthen the navies and coast guards of regional states to assist in countering pirate attacks. Notably, the Italian Military Support Base in Djibouti contributed, utilizing naval vessels such as the Italian Francesco Mimbelli and San Marco in the Gulf of Aden, Indian Ocean, and off the coast of Somalia. Additionally, China, Japan, and South Korea sent warships to participate in these activities.

The United States Navy was the largest contributor of ships, followed by the Indian Navy. The taskforce was composed of ships from the contributing navies, led by a designated leadship. The role of leadship was rotated among the various countries involved.

Pirate attacks off the vast coastline of Somalia declined from 236 in 2011 to two reportedly unsuccessful attacks in 2014, thanks to international counter-piracy cooperation efforts as well as armed guards now stationed on most large ships that traverse the region's waters. NATO has indicated that while it will be ending its mission in the Indian Ocean, the organization "will remain engaged in the fight against piracy by maintaining maritime situational awareness and continuing close links with other international organization's counter-piracy actors." NATO has been supporting international efforts to combat piracy in the Indian Ocean, as well as in the Gulf of Aden and off the Horn of Africa since 2008, at the request of the United Nations. It had been working alongside other missions including the European's Union's Operation Atalanta, the US-led Combined Task Force 151 and other individual countries such as China, Japan, and South Korea."

NATO's success in the area was due in part to the co-operation of other foreign states with interests in the region. A lot of these informal connections took place at SHADE (Shared Awareness and Deconfliction) meetings. These meetings allowed for shared tactics among a large number of international entities, including China, Japan, Russia, India and South Korea but is definitely not limited to them. With NATO promoting co-operation amongst these foreign entities, Operation Ocean Shield could effectively protect the area. They also utilized EUNAVFOR’s innovative electronic network called Mercury which shared anti-piracy tactics with other task forces and operations. Since this was an informal system, it wasn't weighed down with bureaucracy and could be spread amongst other coalitions and governmental organisations and could effectively help anyone that needed precise information in the area.

On 10 January 2010, Admiral Pereira da Cunha, of the Portuguese Navy held a meeting regarding piracy with the Puntland coast guard. It was held aboard the frigate NRP Álvares Cabral near Bosaso, Somalia and focused on human intelligence gathering, capacity building and counter piracy co-operation between NATO and Puntland authorities.

Pirates attacked the Panamanian flagged merchantman MV Almezaan on 25 March. One pirate was killed by Almezaan's crew during the boarding, and shortly afterwards the Spanish Navy frigate Navarra arrived and launched a helicopter. Warning shots were then fired and the pirates surrendered without further conflict. Six pirates were taken prisoner for a short time before being released in two skiffs; the mother ship was sunk by gunfire.

The small Seychelles Coast Guard patrol boat Topaz engaged in another battle with pirates five days later on 30 March. While patrolling just off the coast of Somalia, Topaz encountered a captured dhow. After warning shots were fired, the dhow seemed to ignore the patrol boat and its occupants eventually opened up with rocket-propelled grenades and small arms fire. The Seychellois then engaged and after shooting off 10,000 rounds of machine gun fire, the dhow was burning and eventually sank. Twenty-seven members of the dhow's crew were rescued and the Topaz was returning to base when she was attacked by a trawler and two skiffs. Again the Seychellois responded with counter battery and the trawler exploded. One of the skiffs was sunk as well. Pirate casualties are unknown and one member of the dhow's crew was wounded.

The frigate USS Nicholas was attacked by small arms from a pirate skiff while steaming off the coast of Kenya and the islands of Seychelles. Nicholas returned fire with a 50-caliber deck gun and disabled the vessel and three pirates surrendered. Commander Mark Kesselring ordered the skiff sunk and proceeded to attack the nearby pirate mother ship from which the skiff was operating. After a chase the mothership was captured and two more pirates were taken into United States Navy custody. The pirate mothership was likely a small steam powered vessel fitted out as a naval trawler which are regularly used by Somali pirates. The ship was confiscated by the Americans according to news reports and pirates were put in Nicholas' brig, to await court either in Kenya or the United States.