The 37-year-old, who is engaged to Brad Pitt and raises six kids with him, replaced her giant platinum engagement sparkler with the band, sparking rumours that she has tied the knot with Pitt, reported Us magazine.
The "Maleficent" actress and special envoy of the United Nations' refugee agency was in Africa with British Foreign Secretary William Hague to raise awareness of war zone rape in the Congo and Rwanda.
Earlier Pitt and Jolie had said that they wouldn't tie the knot until the ban on gay marriage would be lifted, but in January 2012, the actor hinted that they had changed their minds.