MSSA may refer to:
Member of the Order of the Star of South Africa Methicillin-sensitive Staphylococcus aureus, a subspecies of bacterium Military Selective Service Act, a law establishing the current Selective Service System in the United States Military-style semi-automatic, a firearm (abbreviation commonly used in New Zealand) Mind Sports South Africa Montreal Student Space Associations MSSA Chemical company, a French chemical company, also known as Métaux Spéciaux Master of Science in Social Administration, master's degree from the Mandel School at Case Western Reserve University, equivalent to a master of social work Multi-channel/-variate Singular spectrum analysis, an extension of the SSA technique