**Northern Star Resources Slashes Output Forecast Amid Operational Headwinds; Shares Tumble**

Investors in Northern Star Resources Ltd (NST.AX) faced a sharp selloff following the company's operational update for the December 2025 quarter. The stock plummeted A$2.99 to A$23.74, marking an 11.19% decline as the market digested disappointing production metrics and downward guidance revisions.

**Production Guidance Trimmed Significantly**

The Australian gold miner substantially reduced its annual output expectations, now targeting 1.600 million ounce to 1.700 million ounce compared to its previous forecast range of 1.700 million ounce to 1.850 million ounce. This adjustment reflects mounting operational challenges that intensified during the final weeks of the December quarter.

**Quarterly Performance Falls Short**

Gold sales for the quarter reached approximately 348 thousand ounce, a result dampened by multiple disruptions hitting the company's operations late in the period. The first-half fiscal 2026 cumulative sales totaled around 729 thousand ounce. Beyond previously disclosed production constraints at Jundee and South Kalgoorlie—which combined to suppress output by up to 20 thousand ounce—unplanned maintenance activities and operational complications further pressured results across all three production centers.

**Cost Pressures Mounting**

With gold sales declining uniformly throughout the company's production network, cost performance is expected to deteriorate. Northern Star Resources will provide comprehensive December quarter cost figures and updated full-year cost projections as part of its quarterly earnings announcement scheduled for Thursday, 22 January 2026.

The sharp equity market reaction underscores investor concern over the sustainability of the miner's production profile and profitability amid an increasingly challenging operational environment.