Southby has stepped down in wake of Netball New Zealand's Independent Review of the 2018 Commonwealth Games campaign.
The Ferns missed out on a medal in Australia after losing to Malawi, England, Australia and Jamaica.
Southby was widely criticised for her selections and rotation strategy, while her record of winning just six of 18 games across the Ferns' most recent international season (including 11 straight losses to Tier One nations Australia, England and Jamaica) led to calls for her sacking.
Further confirming New Zealand's recent demise in the netball world, the Ferns fell out of the top two of the Netball Federation rankings this month for the first time since the rankings began in 2008.
"Earlier today I accepted Janine Southby's resignation from her role as Silver Ferns head coach," said Netball New Zealand CEO Jennie Wyllie.
"I am very sad to have reached this point," Southby said today.
"We were at a real point of transition when I was appointed and I believed it would take time to make the necessary change.
"Over the last two years I have worked hard to develop a high performance culture based on accountability and self-responsibility. I felt we were making steps in the right direction however, I have to acknowledge this hasn't happened as quickly or as well as I would have liked.
"The results we were able to deliver through the transition were unacceptable and far less than what we were aiming for. As head coach, I have to front up to my own responsibility in producing those results and I have. I'm as gutted as anyone that we couldn't produce the results we aimed for."
The process to appoint a new Silver Ferns head coach will commence immediately.
