Who is the Speak of the United States House of Representatives?

On the floor of the House, the presiding officer is always addressed as "Mister Speaker" or "Madam Speaker" (even if the Speaker him or herself is not the individual presiding). When the House resolves itself into a Committee of the Whole, the Speaker designates a member to preside over the Committee as the Chairman, who is addressed as "Mister Chairman" or "Madam Chairman."