Christiane will then review our financial results for the fourth quarter and the full year of 2025 before providing guidance for the first quarter and full year of 2026. Our GAAP results and GAAP to non-GAAP reconciliations are located in our earnings press release and in the presentation that accompany today's remarks, both of which are posted on our Investor Relations website. The prepared remarks will also be posted on the quarterly earnings section of our Investor Relations website following today's call. Lastly, all references to growth are on a year-over-year basis unless noted otherwise.
Driven by broad-based demand across our platform, our billings increased 18% and revenue growth 15%, driven by product revenue growth of 20%. Our operating margin was strong at 37%, reflecting our continued focus on balancing growth and profitability. Secure Networking billings growth 13%, outperforming the overall secure networking market as we continue to gain market share. Fortinet remains the number one firewall leader with 55% unit market share and the highest product revenue among our cybersecurity peers.
Unified SASE billing growth 40%, representing 27% of the total billing, supporting our belief that Fortinet is the fastest growing SASE leader on the scale. Sovereign SASE enables enterprise and service providers to deploy SASE in their own data centers to meet data privacy, sovereignty, and compliance requirements. We are seeing strong demand in sovereign SASE, and none of our major SASE competitors offer sovereign SASE solutions, making Fortinet's total unified SASE addressable market significantly greater than our peers. AI-driven SecOps billings growth 6% in the fourth quarter and 22% for the full year, while ARR was up 21%.