His Holiness Hadhrat Mirza Masroor Ahmad, Khalifatul Masih V performed the ceremony at Ballybrit.
He said he hoped the opening of the mosque would help contribute to interfaith dialogue and understanding and would foster a sense of peace, harmony and tolerance in our societies.
The ceremony was attended by representatives of others faiths and by local politicians.
Galway has had a small Ahmadiyya Muslim Community for the past 30 years.
The movement was founded in 1889 and now has a worldwide membership of over 160m.
