A Vicar Apostolic was appointed to Congo in 1518, but as he was never able to go there and start his ministry, it would be inaccurate to describe Congo as more than an intended Apostolic Vicariate. This Vicar Apostolic, who was ordained a Bishop, was a native of the area.
The area understood by Congo is the northern parts of modern Angola, and the coastal regions of the two modern Congo states.
The Encyclopedia Britannica (1917) states in it's article about Congo: "The evangelization of the Congo began as early as 1484, when Diego Cam discovered the mouth of the Congo River, known as Zaire until the seventeenth century. Cam's naval chaplain set himself at once to preach the "good news" to the natives, and won to the Faith the chief of the Sogno, a village on the right bank of the Congo, where he first landed. Some of the inhabitants of this village accompanied Cam on his return voyage and were solemnly baptized at the court of John II of Portugal. Later, the head chief of the Banza-Congo (Outeiro, the present San Salvador) asked King John for missionaries. Three were sent (whether they were Dominicans or Franciscans or members of a Lisbon chapter we do not know); they finally baptized the head chief and many other subordinate ones at Banza-Congo, in a wooden structure called the Church of the Holy Cross. In 1518, a grandson of this chief, known as Henry, who had been ordained in Portugal, was made titular bishop of Utica, and appointed by Leo X Vicar Apostolic of Congo. Unfortunately, he died before quitting Europe. He is the only native bishop Congo has ever had."