Mōri Yoshikatsu served as a bushō during the Sengoku and Azuchi-Momoyama periods. He was a retainer of the Oda clan.
Although his family origins are uncertain, Yoshikatsu originated from Owari Province. He served as a member of the cavalry for Nobunaga, and may have started as a koshō, or assistant to senior bushō. There are historical documents with his name and seal.
In the fifth month of 1560, during the Battle of Okehazama, Yoshikatsu assisted Hattori Kazutada after Kazutada sustained injuries. Yoshikatsu gained renown for taking the head of Imagawa Yoshimoto in the battle. One of his fingers was severed in the attack. After the battle, he adopted the name of Yoshikatsu and changed his common name from Shinsuke to Shinzaemon.
Yoshikatsu is known as one of the elite warriors selected to have a black horo, a canopy that would inflate on the back of cavalry soldiers and serve to deflect arrows and rocks hurled at them during battle.
After Nobunaga marched upon Kyōtō, in 1569, Yoshikatsu joined in the Siege of Ōkawachi Castle primarily as a messenger. As a close associate of Nobunaga, he served with a cavalry division known as the sakukiwamawari-banshū.
In 1582, Yoshikatsu accompanied Nobunaga during the Invasion of Kōshū. In on deployment in Suwa in the fourth month, he received a gift from the Daijō monastery at the Kōfuku Temple.
In the sixth month of 1582, Nobunaga unexpectedly died in a coup d’état orchestrated by Akechi Mitsuhide known as the Honnō Temple Incident. At this time, Yoshikatsu was lodging in Kyōtō, and after the coup, took refuge in the Nijō palace with Nobunaga’s eldest son, Oda Nobutada, but died in the ensuing attack.