It is an enormous list and depends upon what length of time you give to the Middle Ages.
Saint Thomas Aquinas is called the Angelic Doctor - not because it sounds cute - but in reference to his intellect. He had an angelic intellect, which is to say the Church believes “his learning can only be explained by admitting a miracle,” as Pope John XXII said. It means his intellect was superhuman as the angels’ intellects are far superior to man’s intellect. The Saint’s mentor himself was also a notable genius.
Starting with the lives and stories of such men, or their biographies, you can often find mentioned a great many others who preceded them or were their contemporaries. Naturally more would arise later and the Church has always had her lights.
Roman Catholics frequently suffer from an embarassment of riches.
