What is the full name of Michael Phelps?

The full name of the swimmer is Michael Fred Phelps II. He was born Michael Fred Phelps on June 30, 1985, in Baltimore, Maryland, and is widely known publicly simply as Michael Phelps.

The suffix “II” is part of his formal name, not “Jr.” A junior usually shares the exact name of his father, while “II” can be used when a child is named for another relative or when a family wants to distinguish generations. This is why Michael Fred Phelps Jr. is not the canonical answer to the question.

Phelps became one of the most decorated athletes in Olympic history. Across four Olympic Games, from Sydney 2000 through Rio 2016, he won 28 medals, including 23 golds. His public identity is strongly associated with swimming records, but his full legal-style name appears in biographies, official records, and reference listings as Michael Fred Phelps II. The Roman numeral is therefore an important part of the complete answer.