In a statement to the ASX on Monday, Northern Star said it had "received, considered and rejected a confidential, opportunistic, unsolicited and conditional non-binding indicative proposal from Gold Fields."
The proposal implied an equity value of $38.7 billion, a 22 per cent premium to Northern Star's closing share price on September 11 and a 15 per cent premium to its 30-day volume-weighted average price.
The rejection comes amid pressure from activist investor Elliott Investment Management, which this year criticised the miner's underperformance and called for a sale or asset divestments, as well as an overhaul of the board. Northern Star appointed a new chief executive in July.
The Northern Star board said it considers the company "uniquely positioned" with a portfolio of high-quality, long-life gold assets in tier-1 mining jurisdictions, and pointed to the near-term catalyst of commissioning and ramp-up of the Fimiston Mill.