James Watt is the famous Scottish inventor credited with the invention of the steam engine. Although earlier forms of steam engines existed, Watt improved the design in the late 18th century, making them more efficient and practical for various applications. His innovations included the separate condenser, which significantly reduced energy waste. Watt's advancements facilitated the Industrial Revolution by enabling machines to power factories, trains, and ships, revolutionizing industries and transportation. His work laid the foundation for steam power, which became a driving force in transforming economies and societies during the 19th century and beyond.