From 1960 to 1963, Elizabeth II was Queen of Nigeria: Nigeria was an independent constitutional monarchy.
She was also the monarch of the other Commonwealth realms, including the United Kingdom.

The Federation of Nigeria had superseded the Colony and Protectorate of Nigeria within the British Empire on 1 October 1954.
The Federation was initially a quasi-federal British colony.
It became independent as a dominion within the Commonwealth of Nations on 1 October 1960 under the Parliament of the United Kingdom's Nigeria Independence Act.
The Queen was head of state, though her constitutional roles in Nigeria were mostly delegated to the Governor-General of Nigeria.

The retention of the monarchy was unpopular with Nigerians, and all political parties in Nigeria agreed that the country should be a republic.
Nigeria severed its relationship with the British monarchy, and adopted the President of Nigeria as head of state, on 1 October 1963, when the Federation of Nigeria became the Federal Republic of Nigeria, a republic within the Commonwealth.

The Queen visited Nigeria twice: 28 January–16 February 1956 and 3–6 December 2003, the latter time to attend the Commonwealth Heads of Government Meeting 2003.
From 1960 to 1963, Elizabeth II was Queen of Nigeria: Nigeria was an independent constitutional monarchy. She was also the monarch of the other Commonwealth realms, including the United Kingdom.
The Federation of Nigeria had superseded the Colony and Protectorate of Nigeria within the British Empire on 1 October 1954. The Federation was initially a quasi-federal British colony. It became independent as a dominion within the Commonwealth of Nations on 1 October 1960 under the Parliament of the United Kingdom's Nigeria Independence Act. The Queen was head of state, though her constitutional roles in Nigeria were mostly delegated to the Governor-General of Nigeria.
The retention of the monarchy was unpopular with Nigerians, and all political parties in Nigeria agreed that the country should be a republic. Nigeria severed its relationship with the British monarchy, and adopted the President of Nigeria as head of state, on 1 October 1963, when the Federation of Nigeria became the Federal Republic of Nigeria, a republic within the Commonwealth.
The Queen visited Nigeria twice: 28 January–16 February 1956 and 3–6 December 2003, the latter time to attend the Commonwealth Heads of Government Meeting 2003.
Queen of Nigeria