Which Ottoman sultan had the longest reign?

Suleiman I had the longest reign of any Ottoman sultan. He ruled from 1520 until 1566, a span of nearly 46 years, and is often called Suleiman the Magnificent in English-language histories.

His reign is regarded as a high point of Ottoman power. Ottoman armies captured Belgrade in 1521, Rhodes in 1522, and most of Hungary after the Battle of Mohács in 1526. Suleiman also campaigned against the Safavid Empire and expanded Ottoman influence across the Mediterranean, Iraq, and North Africa.

The answer is sometimes confused with Selim I, Suleiman's father, whose short reign dramatically expanded the empire by conquering Syria, Egypt, and the Hejaz. Suleiman was also a major lawgiver and patron of architecture: the architect Sinan designed major works for him, including Istanbul's Süleymaniye Mosque. Suleiman died during the Siege of Szigetvár in 1566.