Alexios I (1810 - 1865) was King of Nicaea and Co-Regent of Constantinople from 1823 to 1865. He was the oldest son of Romanos I and his wife Theodora Psellina, and older brother and predecessor of Romanos II. He married Zoe Marina, and had a son with her called Ioannes, who would die before succeeding to the throne. Alexios died in 1865, and was succeeded by his younger brother, who became Romanos II.