Leonard Hofstadter is a fictional character from the popular television sitcom The Big Bang Theory. Portrayed by actor Johnny Galecki, Leonard is a physicist with a Ph.D. who often finds himself navigating the complexities of friendship and romance, particularly with his on-again, off-again girlfriend, Penny. His character is known for his nerdy charm and his struggles with social interactions, which often lead to humorous situations. As one of the main characters, Leonard serves as a bridge between the geeky world of science and the more mainstream culture represented by Penny. His relationships with fellow scientists, including Sheldon Cooper and Howard Wolowitz, highlight the dynamics of friendship and intellectual rivalry, making him a relatable figure for many viewers.