Marthas are a class of women in the Republic of Gilead. They serve as domestic servants to wealthy or high-ranking families.
Marthas usually wear green outfits, often with an apron over the top. They also wear headscarves to cover their hair.
Marthas serve as servants, and housekeepers. They clean the houses, go shopping, and cook and serve meals for the high-ranking family they've been assigned to. Most Marthas seem to be infertile, low-ranking, and unmarried women. It is also implied that most Marthas are ethnic minorities, such as Latina, or African-American, displaying Gilead's further discrimination against women who belong to minority groups; in the television series, one of the featured Marthas, Rita, is herself played by a woman of color. Marthas are sometimes assisted in their tasks by their household's Handmaid. They provide food for the Handmaids as well.
Marthas often gossip amongst each other, and are usually quite friendly with each other. It is even implied that they have a communication network of their own. They can be somewhat prejudiced, and derogatory, towards Handmaids, though. If the Wife they serve has children, then Marthas may help in the rearing, acting as a nanny. Many Marthas look forward to this, because, among other reasons, it may be the only chance they will have to raise a child as if it were their own.
It is implied by Offred that if a Martha lives past her "prime", she is sent to The Colonies, where she is ensured certain death.