The String of Pearls is a geopolitical hypothesis proposed by United States political researchers in 2004. The term refers to the network of Chinese military and commercial facilities and relationships along its sea lines of communication which extend from the Chinese mainland to Port Sudan in the Horn of Africa. The sea lines run through several major maritime choke points such as the Strait of Mandeb, the Strait of Malacca, the Strait of Hormuz, and the Lombok Strait as well as other strategic maritime centres in Somalia and the littoral South Asian countries of Pakistan, Sri Lanka, Bangladesh, and the Maldives.

Many commentators in India believe this plan, together with the China–Pakistan Economic Corridor and other parts of China's Belt and Road Initiative under Chinese Communist Party general secretary Xi Jinping, is a threat to India's national security. Such a system would encircle India and threaten its power projection, trade, and potentially territorial integrity. Furthermore, China's support for India's traditional enemy of Pakistan and its Gwadar Port is viewed as a threat, compounded by fears that China may develop an overseas naval military base in Gwadar, which could allow China to conduct expeditionary warfare in the Indian Ocean Region. From the east, the deep-water port of Kyaukpyu is also viewed with a similar concern. The first comprehensive academic analyses of Chinese plan and its security implications for New Delhi was undertaken in February 2008 by an active-duty Indian naval officer. Antedating China's anti-piracy naval deployment in the Indian Ocean beginning in December 2008, and the ensuing acquisition of its first overseas military base in Djibouti in August 2017, his analysis predicting China's "permanent military presence" in the Indian Ocean is viewed by Indian policymakers as prescient. Accordingly, India has since been making moves of various types to counter the threat.

The term as a geopolitical concept was first used in an internal US Department of Defense report, "Energy Futures in Asia" in 2005. The term is also widely used in India's geopolitical and foreign policy narratives to highlight India's concerns over massive Chinese Belt and Road Initiative projects across southern Asia. According to the EUISS, the formation of Quadrilateral Security Dialogue (consisting of Australia, India, Japan, and the United States) is a direct result of China's assertive foreign and security policy in the Indo-Pacific region.

The emergence of the String of Pearls is indicative of China's growing geopolitical influence through concerted efforts to increase access to ports and airfields, expand and modernise military forces, and foster stronger diplomatic relationships with trading partners. The Chinese government insists that China's burgeoning naval strategy is entirely peaceful and is only for the protection of regional trade interests. Chinese Communist Party general secretaries Hu Jintao and Xi Jinping have both asserted that China will never seek hegemony in foreign relations. A 2013 analysis^[update] by The Economist also found the Chinese moves to be commercial in nature. Although it has been claimed that China's actions are creating a security dilemma between China and India in the Indian Ocean, that has been questioned by some analysts, who point to China's fundamental strategic vulnerabilities.

In the theory, a "pearl" refers to a current or potential Chinese overseas military base, mega infrastructure project, economic corridor, port or other city or locale of Chinese geostrategic advantage in the region. These "pearls" are designated by U.S. and Indian strategists. The eponymous "string" of these pearls refers to the possibility of the Chinese Navy connecting these pearls via maritime routes. Chinese political researchers do not use the term String of Pearls to describe their own geopolitical and diplomatic strategy, instead called the term "malicious defamation" from the United States.

In 2004, the U.S. consulting firm Booz Allen Hamilton came up with the "string of pearls" hypothesis, which posits that China will try to expand its naval presence by building civilian maritime infrastructure along the Indian Ocean periphery. According to Pacific Forum researcher Virginia Marantidou, China held great anxiety toward its security environment in the Indian Ocean, due potential U.S. and Indian blockade at the Malacca Strait. This situation, coined the "Malacca dilemma" by Chinese researchers, posed significant challenges to the government elites in Beijing. David H. Shinn predicted in 2008 that China will need to expand their naval capacities in order to protect supply lines of vital resources from Africa and the Middle East to China. American, European, and Indian political strategists have used the term to designates China's point of influences in Indo-Pacific region.

China's rapid economic development over the course of the last quarter century has been heavily dependent on foreign sources of energy, and it is likely that foreign sources of energy will prove even more critical to the continued growth of the Chinese economy. The sea lines of communication that link the Chinese mainland with ports throughout the Middle East and coasts of Africa have become a major source of conflict with respect to China's energy security.

China is the world's largest oil consumer and the largest oil importer. Oil imported from the Gulf States and Africa comprises 70% of total Chinese oil imports, and remains China's most critical source of energy apart from domestic coal burning and nuclear power. To meet future demand, China has signed a number of long-term contracts to develop Iranian oil fields and to build a pipeline, refinery, and port in Sudan for oil export.