The Mother Cathedral of Holy Etchmiadzin is the most recognized landmark of the Armenian Church. Built and consecrated by St. Gregory the Illuminator and St. Trdat the Great in 303 AD, the Cathedral is located in the city of Vagharshapat.

Located on the grounds of the Mother See are the spiritual and administrative headquarters of the worldwide Armenian Church, and the residence of His Holiness Karekin II, Catholicos and Supreme Patriarch of All Armenians.

St. Gregory chose the location of the Cathedral in accordance with a vision that he had. In his dream he saw  «Miatsin» , the Only Begotten Son of God, with glittering light on his face descending from the Heavens and with a golden hammer striking the ground where the Cathedral was to be located. Hence comes the name «Etchmiadzin» which translates literally to "the place where the Only-Begotten Son
of God descended.

The original church was built in the early fourth century between 301 and 303 according to tradition—by Armenia's patron saint Gregory the Illuminator, following the adoption of Christianity as a state religion by King Tiridates III. It replaced a pre-existing temple, symbolizing the conversion from paganism to Christianity. Vahan Mamikonian built the core of the current building in 483/4 after
the cathedral was severely damaged by Persian invasion. From its foundation until the second half of the fifth century, Etchmiadzin was the seat of the Catholicos, the supreme head of the Armenian Church.

Although never losing its significance, the cathedral subsequently suffered centuries of virtual neglect. In 1441 it was restored as Catholicosate and remains as such to this day. Since then the Mother See of Holy Etchmiadzin has been the administrative
headquarters of the Armenian Church. Shah Abbas I of Persia plundered Etchmiadzin in 1604, when relics and stones were taken out of the cathedral in an effort to undermine Armenians attachment to their land. Since then the cathedral has undergone a number of renovations, with Belfries being added.

The Mother Cathedral is open to the faithful everyday from 7:00 a.m. until 8:00 p.m. Divine Liturgy is celebrated every Sunday starting at 11:00 a.m., except on Feast Days or special occasions when it starts at 10:30 a.m. Morning services are conducted starting at 7:30 a.m. Monday through Saturday and at 8:00 a.m. on Sunday. Evening Services are conducted at 5:30 p.m. every day.