Santa Maria degli Angeli e dei Martiri
He played an important part in the First Vatican Council of 1870, being, with George Strossmayer, Bishop of Diakovár, one of the foremost opponents of the dogma of papal infallibility, although he submitted to the decree of the council. Pope Leo XIII made Haynald a cardinal on 12 May 1879. Pope Leo gave him his red galero and assigned him the titular church of Santa Maria degli Angeli e dei Martiri on 22 September.