MIAA may refer to:

• Maine Intercollegiate Athletic Association, defunct athletic conference of schools in Maine
• Manila International Airport Authority, transportation agency in the Philippines
• Maryland Interscholastic Athletic Association, high school athletic conference for private schools in the Baltimore Metro area
• Massachusetts Interscholastic Athletic Association, high school athletic association governing 33 varsity sports throughout Massachusetts
• Michigan Intercollegiate Athletic Association, athletic conference of NCAA Division III schools in Michigan and Indiana
• Mid-America Intercollegiate Athletics Association, athletic conference of NCAA Division II schools in Kansas, Missouri, Nebraska, and Oklahoma
• TRNA dimethylallyltransferase, an enzyme