Introduction: There is an over-reliance on operative time as a surrogate marker for operative difficulty (OD) for liver resection, which fails to capture the full spectrum the procedure. This study aimed to develop an objective method to assess OD in liver resection and stratify quality outcomes based on OD. Methods: A retrospective review of patients undergoing liver resection for malignant disease between 1999-2023 at a tertiary hospital was completed from a prospectively collected database. Principal component analysis was applied to operative time, estimated blood loss, total time of hepatic inflow occlusion and number of units of blood transfused intraoperatively to derive an OD score using the z-score. Patients were stratified to three groups using Gaussian mixture models (GMM). Textbook oncological outcomes (TOO) and futile resection rates were compared using Chi-squared analysis. Subgroup analysis for overall survival (OS) and disease-free survival (DFS) was completed using the Kaplan-Meier method. Results: Of 729 patients, 699 met the inclusion criteria. GMM identified three distinct OD groups: low (n=540), moderate (n=143), and high (n=16). TOO and non-futile resection rates declined with increasing OD: 77% and 58% (low), 47% and 52% (moderate), and 6% and 19% (high), respectively (p<0.001). Among patients with cholangiocarcinoma, median OS was inversely correlated with OD (40 months low, 16 months moderate, 7 months high, p=0.004). In patients with colorectal liver metastases, there was a trend towards worse OS and DFS with increasing OD, however, this did not reach statistical significance. Conclusion: An objective OD score was developed that showed increasing OD was associated with poorer post-operative outcomes. Integrating the OD score supports more transparent, data-informed surgical decision-making and helps align expectations between teams and patients. Further external prospective studies are required to validate these findings.