Modern smart grids encounter several challenges, including the variability of renewable energy sources with power fluctuations of ±35% in solar farms across the Arabian Gulf countries, delays in centralized control, with latencies of 150–200 ms, including all time needed from sending data to receiving control commands, and increased susceptibility to cyber threats, with a 30% annual increase in grid intrusions. Incorporating renewable energy into smart grids presents significant challenges, including intermittent generation, characterized by ±30% solar volatility, slow fault detection, and response times exceeding 500 ms in traditional systems, as well as centralized system weaknesses. This paper presents SwarmNet-5G, a bio-inspired neural network that integrates stigmergic learning and spiking neural networks (SNNs) for decentralized grid management to resolve existing issues. It merges Internet of Things (IoT)-edge intelligence, spiking neuromorphic computing, and swarm-based stigmergy to enable grid optimization. Its design decreases latency by 40% compared to typical deep reinforcement learning (DRL). It achieves a fault detection accuracy of 99.62% within 8.17 ms and requires 50 ms for repair, aligning with Saudi Arabia's Vision 2030 goal of achieving 50% renewable energy. Simulation results performed on the IEEE 39-bus using a dataset show that the solution allocated power during peak demand, such as a 20% load increase, with an efficiency of 92%, while typical DRL reached 78%. Additionally, the model projected annual savings of.2B in maintenance costs and a reduction of 4.8 megatons in CO₂ emissions per year.