Ueshiba (pronounced 'oo-eh-she-ba') was born in the Wakayama Prefecture on December 14, 1883 in a Japan which had not fully emerged into the modern world and where many of the martial arts were still taught by masters in the old tradition. As a boy, he often witnessed local thugs assault his father for political reasons and so he set out to make himself strong so that he could take revenge.

In 1898, 15 year-old Ueshiba left his home village of Tanabe outside Osaka and traveled to Tokyo, seeking instruction in the martial arts. In the following years he studied jujutsu, kenjutsu, and judo, eventually earning teaching certificates in judo and Daito-Ryu jujutsu (see Sokaku Takeda). In spite of his impressive physical and martial capabilities, however, he felt very dissatisfied. He began delving into religions in hopes of finding a deeper significance to life, all the while continuing to pursue his studies of budo, or the martial arts. By blending elements of each of these arts, along with the spiritual traditions of Shinto, Buddhism and specifically Omotokyo (see Onisaburo Deguchi), he formed the backdrop to the creation of what is known today as Aikido.

The formulation of Aikido dates from a legendary incident that occurred in 1925. In early 20th-century Japan, involvement in the martial arts was a competitive and dangerous business. Contests, feuds and rivalries often resulted in injuries and even deaths. In the course of a discussion about martial arts, a disagreement arose between Ueshiba and a naval officer who was a fencing instructor.

 The officer challenged Ueshiba to a match, and attacked with wooden sword. Ueshiba faced the officer unarmed, and won the match by evading blows until his attacker dropped from exhaustion. He later recalled that he could see opponent's moves before they were executed, and that this was the beginning of his enlightenment. He had defeated an armed attacker without hurting him - without even touching him. Ueshiba felt that the very desire to attack breaks the harmony of the universe and is therefore a weakness. He realised that the true aim of the martial arts should be protection, not destruction. "True budo (martial arts) is love," he said, and that meant that one should even try to protect one's attacker. This was a truly radical shift in traditional martial arts philosophy. That he meant Aikido to be more than a method of self-defence is conveyed in his words, "I want considerate people to listen to the voice of Aikido. It is not for correcting others; it is for correcting your own mind".

Originally referred to as Aiki bujutsu, Ueshiba's "new" martial art diverged from classical styles and forms in several important ways. First, the use of the term "aiki" in this context denoted a more profound emphasis on harmonizing with the energy of the attacker than any martial art that preceded it. "Ai" refers to matching, blending with, or harmonizing with, and "ki" refers to the fundamental life force that pervades all beings and the entire universe. Second, the change from "bujutsu" to "do" indicates a move away from just techniques and more toward a martial "way". From 1942 (when the name Aikido was first formally used) to 1952, Ueshiba consolidated the techniques and perfected the religious philosophy of Aikido.

Before World War II, Aikido was practiced by only a few people. One needed an introduction even to be considered for admittance as a student. But with the lesson of war fresh in his mind, Ueshiba opened the practice of Aikido to the general public in the late 1940's, hoping that his art might help to contribute to greater social and personal harmony. In 1942, supposedly because of a divine command, he returned to the Ibaraki farmlands, moving to the village of Iwama where he built the outdoor Aiki Shuren Dojo and the now famous Aiki Shrine. He often said “Budo and farming are one”. Today, Iwama is considered by many to be the birth place of modern-day Aikido. It was during the following years that Ueshiba came to be known as O'Sensei (great teacher) by his students. Right up to the end of his life, O'Sensei refined and improved his "way", never losing his dedication for hard training.

While visiting Tokyo in 1969, O'Sensei fell ill and told his son Kisshomaru that "God is calling me....". He was returned to his home in the village of Iwama at his request to be near his dojo.

On April 15th, his condition became critical. As his students made their last calls, he gave his final instructions. "Aikido is for the entire world. Train not for selfish reasons, but for all people everywhere." Early on the morning of April 26th, 1969, the 86-year-old O'Sensei took his son's hand, smiled and said, "Take care of things" and died. Two months later, Hatsu, his wife of 67 years, followed him.

After he passed away, the Japanese government posthumously declared Morihei Ueshiba a Sacred National Treasure of Japan. O Sensei's ashes were buried in the family temple in Tanabe. Every year a memorial service is held on April 29th at the Aiki Shrine in Iwama.

O'Sensei's son, Kisshomaru Ueshiba, inherited the title "Doshu" (Leader of the Way). After his death in January of 1999, the title was passed on to his son, Moriteru Ueshiba. Today, Aikido is practiced by men, women, and children in over 50 countries. O'Sensei's teachings enlighten the lives of thousands of people all over the world.