In Christianity, the concept of an Apostolic Throne refers to one of the historic Patriarchates that was associated with a specific apostle. Not all of the apostles are associated with specific "thrones"; in general, the phrase applies to Apostles that presided over a specific geographic church. Notably, there is no apostolic throne associated with St. Paul, who along with St. Peter was present, at different times, in both Antioch and Rome (where both Peter and Paul were crucified. The phrase is also somewhat interchangeable with the "Apostolic See".
The See of Milan claimed the Apostle Barnabas as its founder, but this was disputed. Nonetheless, this Apostolic Throne was later occupied by the highly important Bishop St. Ambrose, who was the mentor of St. Augustine of Hippo (not to be confused with St. Augustine of Canterbury) presided over the See of Milan, which follows a distinctive rite, the Ambrosian Rite, with a liturgy somewhat different from that of Latin Rite Catholicism.
The Archbishop of Canterbury is crowned atop St. Augustine's Chair, referring to the first holder of that office, St. Augustine of Canterbury, not to be confused with the earlier theologian St. Augustine of Hippo.