The couple have a 21-month-old son, Ethan, together. Smith reportedly moved out of the couple's home in Melbourne after the pair "fought and fought" to save their relationship.
"It brings me great sadness to tell you that Kris and I have separated. We still care for each other and ask for privacy at this difficult time, in particular for our son Ethan who remains our number one priority," the designer announced the news on Twitter.
Minogue then followed up the tweet by posting to her fans, "Hi Tweet peeps. Needing to retreat for a while. Thank you for your ever loving continued support."
Smith made a similar statement on his Twitter, writing, "Dannii and I have a deep mutual love and respect for each other and although things have not worked out we have a gorgeous son together that we both love and implore everyone to respect our privacy at this challenging time."
