Lourd will guest star on the final season of the resurrected show as Fiona Adler, reports deadline.com.
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"The episode is especially meaningful because of Billie's relationship to the show. We're thrilled to have Billie. And best of all -- she's really good," said "Will and Grace" co-creator and executive producer Max Mutchnick.
Reynolds played Bobbie Adler in 12 episodes from 1999-2006, earning an Emmy nomination in 2000. She passed away in 2016.
The "Will and Grace" revival did a tribute episode following her demise, which featured Grace taking Will back to her family home for her late mother Bobbi's birthday.
Lourd took to Instagram on Thursday to share a series of shots of Reynolds from the show.