LLM Gateways, also known as LLM routers, are essential tools for managing complex AI applications by serving as intermediaries between applications and multiple AI providers. They address challenges like API format differences, provider outages, cost optimization, and performance monitoring, while ensuring low latency. The guide evaluates five leading LLM Gateways: Helicone AI Gateway, OpenRouter, Portkey, LiteLLM, and Unify AI, each offering unique strengths tailored to different use cases. Helicone AI Gateway is highlighted for its speed and robust observability features, OpenRouter for its simplicity and user-friendly interface, Portkey for enterprise-grade controls and security, LiteLLM for its open-source flexibility and advanced routing capabilities, and Unify AI for basic routing needs. These gateways differ in setup complexity, scalability, integration, and pricing, with options ranging from free open-source models to subscription-based services, making them indispensable for achieving efficient, reliable, and scalable AI operations.