Shoghí Effendí Rabbání (March 1, 1897 – November 4, 1957), better known as Shoghi Effendi, was the Guardian and appointed head of the Bahá'í Faith from 1921 until his death in 1957. After the death of `Abdu'l-Bahá in 1921, the leadership of the Bahá'í community entered a new phase, evolving from that of a single individual to an administrative order with executive and legislative branches, the head of each being the Guardianship and the Universal House of Justice. Shoghi Effendi was referred to as the Guardian, and held the explicit authority to interpret the writings of the three central figures of the religion and define the sphere of legislative authority. His writings are effectively limited to commentaries on the works of the central figures, and broad directives for the future.
Future hereditary Guardians were permitted in the Bahá'í scripture by appointment from one to the next, but a prerequisite that appointees be male descendants of Bahá'u'lláh left no suitable living candidates, and Shoghi Effendi died without making an appointment. The Universal House of Justice, the only institution authorized to adjudicate on situations not covered in scripture, later announced that it could not legislate to make possible the appointment of a successor to Shoghi Effendi. To Bahá'ís he is the first and last Guardian.
Read more about Shoghi Effendi: Background, Accomplishments, Translations and Writings, Leadership, Private Life, Unexpected Death