"That there is only One, Holy, Catholic and Apostolic Church we are compelled by faith to believe and hold, and we firmly believe in her and sincerely confess her, outside of whom there is neither salvation nor remission of sins.....Furthermore we declare, state and define that it is absolutely necessary for the salvation of all human beings that they submit to the Roman Pontiff."
POPE BONIFACE VIII Unam Sanctam (November 18, 1302 AD)
If this fails to meet the standard of "infallibility" please enlighten me.
The Unam Sanctam citation would make for a very interesting intra-Catholic discussion. If it was a genuine exercise of infallibility does the degree of submission necessary change with the man holding the office? I mean Benedict seems to have a very relaxed view of what’s required, so too his immediate predecessors.