This document provides an introduction to health policy and systems research (HPSR). It discusses how HPSR seeks to understand how societies organize themselves to achieve health goals and how different actors interact in the policy and implementation process. It emphasizes that HPSR takes an interdisciplinary approach and provides a comprehensive picture of how health systems respond to policies and vice versa. The document outlines the four steps of HPSR research and highlights issues like ensuring substantive relevance, valuing multiple perspectives, research rigor, and ethics. It discusses threshold concepts in HPSR and important skills like framing questions and identifying appropriate study designs.