Labor senator Kimberley Kitching has died suddenly at the age of 52 from a suspected heart attack.
Colleagues and friends have begun sharing tributes on social media, with Labor leader Anthony Albanese saying the party was in shock at the tragic news.
"My sincere condolences to her family. Kimberley will be missed by us all," he said on Twitter.
Former Labor leader Bill Shorten said Senator Kitching suffered from "a heart problem" on Thursday evening in Melbourne and died soon after.
Mr Shorten said her passing was an immense loss to Labor and the nation.
"To know Kimberley was to be touched not just by her serene intellect but her incredible warmth and vivacity," he said in a statement.
"As a Labor senator she was relentlessly energetic and conscientious recently resulting in international recognition for her human rights work.
"Our hearts go out to her husband Andrew, her family and loved ones."
Labor MP Madeleine King wrote about how much she would miss the senator.
"She was a steadfast and supportive colleague. Smart, hardworking, dedicated, funny and fun to be around," she wrote on Twitter.
"I wish I had told her that. I'll miss coffees shared at Aussies & around the building. I'll miss Kimberley."
Prime Minister Scott Morrison also tweeted his condolences, saying he was "deeply saddened" by the shock news.
Liberal MP Tim Wilson called Senator Kitching a "true patriot".
"Devastating. A true patriot. Someone who loved her country and freedom above everything. Just devastating. Complete shock," he wrote on Twitter.
