Abe Masahiro (阿部 正弘^?, December 3, 1819, Edo (now Tokyo) – August 6, 1857, Edo) was the chief senior councillor (rōjū) in the Japanese government at the time of the arrival of Commodore Matthew Perry. Against the shogun's wishes, and the wishes of many other government officials, he worked to open Japan to the West, signing the Convention of Kanagawa in 1854, and other unequal treaties shortly afterwards.

Abe Masahiro was born in his family's residence outside Edo Castle. He was the 6th son of Abe Masakiyo, the 5th lord of Fukuyama. Upon his father's death in 1826, his elder brother Masayasu became lord of Fukuyama; Abe was moved to the domain's naka-yashiki (middle residence) in Hongō, Edo (modern-day Bunkyō, Tokyo). However, in 1836, Masayasu adopted his brother as heir. Abe succeeded to family headship upon his brother's retirement in early 1837, and became lord of Fukuyama, taking the opportunity to make the long journey there.

Abe was appointed a Soshaban (master of ceremony) in 1838; in 1840 Abe received the post of jisha bugyō (minister of shrines and temples). He became rōjū three years later, in 1843, moving his residence to the Abe family's estate at Tatsunokuchi, outside Edo Castle. He became rōjū shuza (老中首座, presiding senior councillor) in the same year, after Mizuno Tadakuni lost his standing over the failure of the Tenpo reforms. Throughout the course the reigns of the 12th and 13th shoguns Ieyoshi and Iesada, Abe worked to unify shogunate politics. He supervised the reconstruction of the western enceinte of Edo Castle in 1852, and was awarded an increase of 10,000 koku in income for this service. In the meantime, he kept the shogunate abreast of foreign political developments, such as the outbreak of the First Opium War.

Masahiro Abe (阿部 真宏, Abe Masahiro^?, born May 12, 1978 in Kawasaki, Kanagawa, Japan) is a Nippon Professional Baseball player. He is currently with the Saitama Seibu Lions in Japan's Pacific League.