The custom-made, shimmering, metallic Prada dress is up for auction to support Oxfam USA and is currently fetching just over €1500.
The dress was put up for auction by the charity last Wednesday evening and the bidding will continue until this Saturday, May 19th.
The halter-style, knee-length dress was worn by the actress last week to attend the Costume Institute Gala in New York City, which celebrated Italian designers Elsa Schiaparelli and Miuccia Prada, the latter dressed Mulligan.
The dress is a custom-fit for Mulligan, in an Italian size 38-40 which is roughly between a UK size 6 and 8. Newly-married Mulligan tied the knot with musician Marcus Mumford last month and attended the event with her husband in tow.
Mulligan performed a similar action with a Vionnet dress she wore to the 2010 BAFTAs.
