The Aikikai is the original school of Aikido. It is centered on the Aikikai Foundation in Japan, and its figurehead is the Doshu (the family heir of the founder of Aikido). It is represented globally through the International Aikido Federation.
Read more about Aikikai: Aikikai Foundation, Doshu, Hombu Dojo, Aikikai School of Aikido, International Aikido Federation, Aikikai Style of Aikido