Which Aztec goddess associated with the Day of the Dead is known as 'Lady of the Dead'?

The Aztec goddess known as the “Lady of the Dead” is Mictecacihuatl.

In Aztec mythology, Mictecacihuatl is a death deity associated with Mictlán, the underworld, and is described as the consort of Mictlantecuhtli, its male ruler. Her name is commonly rendered without diacritics as Mictecacihuatl, while scholarly spellings may use Mictēcacihuātl or other orthographic variations.

Her traditional role was to watch over the bones of the dead and preside over festivals honoring the deceased. These pre-Hispanic observances are often discussed as part of the complex cultural history behind modern Día de Muertos, which also incorporates Catholic traditions introduced during Spanish colonization. That does not mean the modern holiday is simply an unchanged Aztec ceremony; it developed through centuries of cultural blending.

Mictecacihuatl is sometimes confused with Mictlantecuhtli because the two deities are closely connected. The distinction is useful: Mictecacihuatl is the female death deity and “Lady of the Dead,” while Mictlantecuhtli is the male god and ruler of the underworld. She is also distinct from La Catrina, a much later artistic figure.