Reports that the couple tied the knot started to circulate after the two were spotted loved-up in Byron Bay, along with Liam's entire family.
Chris, 34, told SiriusXM's Sway in the Morning, 'They're not officially married.'
The Thor actor also revealed that his future sister-in-law is 'a lot of fun.'
'She’s expected to put on show and bang a few songs out, but she never does,' Chris joked. 'I am insisting constantly. I’m like, ‘When’s the performance coming?’ She’s a lot of fun.'
A source told Us Weekly earlier in the year that the couple were in no rush to walk down the aisle.
'They consider themselves married,' said the source.
It's not the first time that wedding rumours started to spark.
Miley's dad Billy Ray sent fans into a frenzy in March when he shared an Instagram photo of Miley wearing a white dress, with the caption: 'I’m so happy…you are happy.'
Billy Ray was then forced to tweet revealing that Miley wasn't married, and was just wearing white.
The 25-year-old Disney alum and the 28-year-old The Hunger Games star have been dating on and off since they met on the set of the romantic drama, The Last Song in 2010. Liam proposed in May 2012, but they called off the engagement in September 2013. Two years later, the couple got back together and Cyrus was spotted wearing her engagement ring soon after.