China and Japan are geographically separated by the East China Sea. China has strongly influenced Japan with its language,architecture, culture, religion, philosophy, and law. When Western countries forced Japan to open trading in the mid-19th century, Japan moved towards modernization (Meiji Restoration), viewing China as an antiquated civilization, unable to defend itself against Western forces in part due to the Opium Wars and Anglo-French Expeditions from the 1840s to the 1860s.

The relationship between China and Japan has been strained at times by Japan's refusal to acknowledge its wartime past to the satisfaction of China. Revisionist comments made by prominent Japanese officials and some Japanese history textbooks regarding the 1937 Nanking Massacre have been a focus of particular controversy. Sino-Japanese relations warmed considerably after Shinzo Abe became the Prime Minister of Japan in September 2006, and a joint historical study conducted by China and Japan released a report in 2010 which pointed toward a new consensus on the issue of World War Ⅱ-era atrocities. However, in the early 2010s, relations cooled once more, with Japan accusing China of withholding its reserves of valuable rare earth elements. The Diaoyu Islands dispute also resulted in a number of hostile encounters in the East China Sea, heated rhetoric, and riots in the PRC.

China's and Japan's economies are respectively the world's second and third-largest economies. In 2008, China-Japan trade grew to $266.4 billion, a rise of 12.5 percent on 2007, making China and Japan the top two-way trading partners. China was also the biggest destination for Japanese exports in 2009.