Pope Leo VIII (died 1 March 965) was Pope from 23 June 964 to his death in 965; before that, he was an antipope from 963 to 964, in opposition to Pope John XII and Pope Benedict V. An appointee of the Holy Roman Emperor, Otto I, his pontificate occurred during the period known as the Saeculum obscurum.
Due to Leo's uncanonical election, it is now accepted that, until the deposition of Benedict V, he was almost certainly an antipope. Further, although the deposition of John XII was invalid, the election of Benedict V certainly was canonical. However, if Liutprand of Cremona (who chronicled the events of this period) can be relied upon, if, as he wrote, Benedict did acquiesce to his deposition, and if, as seems certain, no further protest was made against Leo's position, it has been the consensus of historians that he may be regarded as a true pope from July 964 to his death in 965. The fact that the next pope to assume the name Leo was consecrated Leo IX also seems to indicate that he is a true pope.