Who abducts Anakin's mother and holds her hostage?

The Tusken Raiders abduct Anakin Skywalker’s mother, Shmi Skywalker, and hold her captive on Tatooine.

In Star Wars: Episode II – Attack of the Clones, Shmi is living at the Lars moisture farm after marrying Cliegg Lars, who previously freed her from slavery. A Tusken Raider party takes her while she is gathering mushrooms in the desert. Cliegg and several farmers attempt a rescue, but the search fails, and Cliegg loses a leg.

Anakin senses his mother’s suffering through the Force and returns to Tatooine with Padmé Amidala. He finds Shmi in a Tusken camp, severely injured after weeks of captivity. She dies in his arms shortly after he reaches her, triggering Anakin’s furious slaughter of the entire camp, including its women and children.

The answer is sometimes confused with “slavers,” because Shmi was enslaved earlier in her life by Watto. The Jawas are also associated with Tatooine, while Ewoks live on Endor; neither group abducts Shmi. Her death becomes a major turning point in Anakin’s eventual fall toward the dark side.