Is South Africa part of Africa?

Yes, the Republic of South Africa (formerly called the Union of South Africa) is a country on the southern tip of the continent of Africa.

In addition, "south Africa," or "southern Africa," describes a region at the southern part of Africa that includes the Republic of South Africa, the Republic of Namibia, the Republic of Botswana, the Republic of Zimbabwe, the Republic of Mozambique, the Kingdom of Swaziland, the Republic of Angola, and the Kingdom of Lesotho.