This week numerous reports emerged saying the music mogul is engaged to marry Mezhgan Hussainy – his girlfriend of six months.
They were first sparked when the makeup artist was seen wearing a ring on her engagement finger, and in light of a recent revealing interview Simon gave to Piers Morgan.
And while the millionaire X Factor judge refuses to comment on reports of his impending nuptials, his co-judge Louis Walsh has been speaking out.
"I'm very surprised but delighted he's got engaged," the Irish music manager told the Mirror. "Mish is a lovely girl. They've been close for a long time but it's only in the last few months that it's got serious."
"She is fantastic for him, very grounding, which is exactly what he needs to keep that ego in check."
Simon's ex-girlfriend, former pop star Sinitta - pictured - has also discussing the happy news.
"They are really in love," said the Seattle-born actress and singer. "She's a really lovely girl. I hope to be a bridesmaid."
Another friend of the 50-year-old – who famously declared he would never marry - told the newspaper: "Simon's asked us all to keep quiet about the engagement because, I think, after everything he's said over the years, he's a bit embarrassed about it."
"He's totally smitten with Mezhgan and knows there's nothing she wants more than to get married with a nice stylish wedding and start a family. It's something his mum would love as well."
"Turning 50 a few months ago made him think seriously about the future."
Simon and the Afghanistan-born 36-year-old first met in 2004 when she began work on American Idol.
After the end of his long-term relationship with Terri Seymour in 2008, Simon declared he was "too busy" for a relationship.
But one year later his romance with divorcee Mezhgan took off and she was the special guest at his lavish birthday celebrations in October.
It's reported that Simon proposed on Valentine's Day with a £250,000 Graft diamond ring.