Twelve months after finishing with the NRL wooden spoon, Newcastle are through to their first Grand Final since 2001.
The Knights beat Penrith 22-14 in a remarkable preliminary final and will face the Sydney Roosters in the 2026 decider.
Newcastle trailed 14-6 at the break, then lost hooker Phoenix Crossland to a send-off for a hip-drop tackle on Nathan Cleary.
Despite playing the entire second half with 12 men, the Knights scored three tries and kept the Panthers scoreless.
Penrith applied patient, direct pressure, but Casey McLean was held up with nine minutes remaining as the Panthers chased the lead.
Newcastle took control in the 58th minute when Sandon Smith exploited Penrith's defence from a quick tap after a Knights penalty, putting his side ahead 16-14 in the rain.
"One of the cheekiest finals tries you've ever seen!" added Andrew Voss.
The Knights held on, then Smith ran in a try in the final minute to seal the victory as Newcastle supporters celebrated.