Lifespan: Eiroku 12 (1569) to 11/14 of Shōhō 4 (1647)
Rank: bushō; daimyō
Title: Junior Fourth Rank (Lower); Governor of Bitchū
Bakufu: Edo – Chamberlain of Ōsaka Castle
Han: Head of Musashi-Hatogaya → head of Kazusa-Ōtaki → head of Sagami-Odawara → head of Musashi-Iwatsuki
Father: Abe Masakatsu
Mother: Daughter of Ebara Sadaji
Siblings: Sister, Masatsugu, sister (wife of Nagai Naokatsu), Masayo
Wife: [Formal] Daughter of Sawara Yoshinari
Children: Masazumi, Shigetsugu, Moritsugu, daughter (formal wife of Naitō Nobuteru), daughter (formal wife of Naruse Yukinari), daughter (wife of Andō Shigemoto)
Abe Masatsugu served as a daimyō during the Azuchi-Momoyama and Edo periods. He was the head of the Hatogaya han of Musashi Province, the Ōtaki han of Kazusa Province, and the Odawara han of Sagami Province, after which he became the first lord of the Musashi-Iwatsuki han. Masatsugu further served as chamberlain for Ōsaka Castle and the first lineal head of the Abe clan.
In 1569, Masatsugu was born as the eldest son of Abe Masakatsu in Mikawa Province. His mother was the daughter of Ebara Sadaji, a retainer of the Imagawa clan. In 1600, Masatsugu succeeded his father as head of the clan, including a fief of 5,000 koku in Hatogaya. In 1610, he moved to Kanuma in Shimotsuke Province.
In 1614, at the Winter Siege of Ōsaka, the advance on Ōsaka Castle stalled for the commanders of several front-line units. Masatsugu fought valiantly while leading an ōbangumishū, or team of elite hatamoto soldiers, to be the first to penetrate the castle defenses and to kill the enemy. Following the battle, the size of his fief increased rapidly so that by 1626 he controlled over 86,000 koku. He was appointed chamberlain of Ōsaka Castle and continued in that capacity for twenty-two years until his death.
In 1637, on the occasion of the Shimabara no ran, or Battle of Shimabara, Masatsugu managed communications and coordination between Edo and Kyūshū. In 1638, Masatsugu assigned a fief of 46,000 koku to his eldest son, Shigetsugu, 10,000 koku to his grandson, Masayoshi, and continued himself to manage a domain of 30,000 koku. Later that year, Shigetsugu was appointed as a rōjū, or elder, in the Tokugawa bakufu.
In 1647, Masatsugu died in Ōsaka Castle while serving his duties as chamberlain.