UImGui is a Unity package that integrates Dear ImGui (immediate-mode GUI library) with the Unity game engine. It provides a complete solution for creating debug UIs, internal tools, runtime overlays, and editor-like workflows within Unity applications. The architecture centers around a UImGui MonoBehaviour that manages the Dear ImGui frame loop, with abstractions for rendering (Mesh vs Procedural), input (Input Manager vs Input System), and optional plugin integrations (ImPlot, ImNodes, ImGuizmo, etc.). The package supports all three Unity render pipelines (Built-in, URP, HDRP) and both Unity input systems, with proper texture handling, font management via FreeType, and docking support.