Literally, the word Doshu (道主 / どうしゅ / Dōshu) means “Master of the Way”. This title is given to the leader of the Aikikai. While the same term can probably be used for members of other schools, in Japanese its most common meaning is used specifically for the Aikido Association.

The system of succession of a martial arts school leader (iemoto) by his son (either biological or adopted due to succession) was common in koryū (traditional schools). Other schools use the title Sōke for the leader.

Founder (開祖 Kaiso): Morihei Ueshiba (1883-1969). He founded the art of Aikido. He was the first Doshu but was often referred to as Osensei (Grand Master).

Second Doshu (二代道主): Kisshomaru Ueshiba (1921-1999). He took over the organization and acquired the title of Doshu in 1969 after the death of his father Morihei Ueshiba. Kisshomaru was the first in the field of Aikido to be often referred to as Doshu. He was succeeded by his son Moriteru.
Third Doshu (三代道主): Moriteru Ueshiba (1951-). He serves as the current Doshu. He is the grandson of the founder of Aikido and acquired the title in 1999.

Moriteru is to be succeeded by his son Mitsuteru Ueshiba (1980-) who is referred to as “Waka(若) Sensei”.