IGA or IgA may refer to:

• IGA (supermarkets) (initially Independent Grocers Alliance), a name used by many independent supermarkets throughout the world
  • IGA (Australian supermarket group), the local Australian variant of the international IGA
• International Island Games Association, an organization that organizes the Island Games (a friendly competition between teams from several islands and other small territories)
• International Grenfell Association, an organization providing health care, education, religious and other services to the fishermen and coastal communities in Newfoundland and Labrador
• Interscope-Geffen-A&M, an American record label
• Irish Games Association, a non-profit body which is dedicated to promoting gaming in Ireland

Iga may refer to:
People:

• Jadwiga (diminutive "Iga"), a female given name of Polish origin
• Iga Cembrzynska, a Polish actress
• Iga Wyrwal (also known as Eva or Eve), a Polish glamour model
• Koji Igarashi (nicknamed "Iga"), a video game producer, known for his involvement with the Castlevania series

Immunoglobulin A (IgA, also referred to as sIgA) is an antibody that plays a critical role in mucosal immunity. More IgA is produced in mucosal linings than all other types of antibody combined; between three and five grams are secreted into the intestinal lumen each day. This accumulates up to 15% of the total immunoglobulin produced in the entire body.