This book introduces the skills and mindset that are introduced during 3 Day Startup educational programs. It covers a wide range of topics encountered by early-stage entrepreneurs, including customer validation, iterative product development, developing preliminary business frameworks, start-up communications and networking, and balancing starting a business with other commitments. The content is actionable, concise, and easy to understand, focusing on pragmatic, applicable skills over dense academic theory and case studies. The information in this volume is easily accessible by entrepreneurs from all walks of life.3 Day Startup is an international non-profit organization that delivers entrepreneurship education in diverse settings around the world. It was founded in 2008 by graduate students at the University of Texas at Austin that wanted better resources for entrepreneurship education than was available at the time. To do this, it pioneered an intensive, extracurricular experiential curriculum that could be applied in highly diverse educational settings. Since its beginnings as a small group of graduate students at UT Austin, it has exploded into the global non-profit it is today. To date, 3 Day Startup has delivered almost 500 educational programs at over 175 different educational institutions in 35 countries worldwide.