Who presided over the Council of Nicaea?

The presiding figure at the Council of Nicaea was Emperor Constantine. He convened the council in 325 AD primarily to address the Arian controversy regarding the nature of Christ and to attain unity within the Christian church. Constantine's involvement was significant, as he sought to establish a degree of orthodoxy and resolve disputes that were creating divisions among Christians.

As an emperor, he recognized the importance of a unified church to maintain political stability within his empire. This council produced the Nicene Creed, which outlined the basic tenets of Christian faith regarding the divinity of Jesus Christ, and it was a crucial step in defining orthodox Christian doctrine.

The other figures mentioned are either from different periods or did not play a role in this specific council. Emperor Augustus and Emperor Nero were long before Constantine's time, and Pope Leo I was not present at the Council of Nicaea as he served later in the 5th century. Thus, Constantine's role as the presider at the council is clearly pivotal to its historical context.