Hosted by his ex and close pal Jackie St Claire the bash should definitely go with a swing.
Heading the list of former flames in attendance is likely to be Terri Seymour, his former love of six years, and Sinitta, his love interest during the Eighties.
His first childhood sweetheart Tara McDonald-Smith has also been invited.
In their company, the TV impresario should have a fabulous time as he's often quoted as saying he thinks of these ladies as family.
"I don't think of them as ex-girlfriends anymore. They are an extension of my life", he explained in one interview.
The bash will feature a performance by Britain's Got Talent finalists Stavros Flatley. The novelty comedy act had Simon in stitches when they appeared on the star search show
Meanwhile all the guests have been instructed to wear white – their friend's favourite colour.
According to the Daily Mirror, Tara has told Simon – who doesn't actually turn 50 until October - that it's for her own birthday to put him off the scent.
A source said: "The champagne will be flowing and judging by the guest list, Simon will need it. Incredibly, 17 of his ex-girlfriends, dates and former flings will be there".
"For most men this would be an utter nightmare, but if anyone can pull it off, Simon can."