The Let Them Theory is a #1 bestselling self-help book by Mel Robbins, co-authored with Sawyer Robbins and published by Penguin Random House (Hay House imprint). With over 8 million copies sold in its first eleven months, it is the top-selling book of 2025 according to Publishers Weekly.

The book introduces a deceptively simple two-word mindset shift — "Let Them" — that teaches readers how to stop trying to control other people's opinions, behaviors, and reactions. Mel Robbins presents a step-by-step guide for applying this concept in eight key areas of life to reduce stress, build better relationships, and reclaim your sense of personal freedom. The approach is grounded in science and draws on insights from Robbins' globally popular podcast, The Mel Robbins Podcast.

Readers learn how to manage stress, overcome the fear of other people's judgments, handle negative reactions with grace, stop chronic comparison, navigate adult friendships, motivate others to change, help people who are struggling, and choose the love they deserve. The book has been praised by Oprah Winfrey, Jay Shetty, Dr. Gabor Maté, and Charlamagne tha God, and was named one of the Best Books of the Year by Amazon, Goodreads, Barnes & Noble, Audible, Target, and Waterstones. ISBN: 9781401971366. Hardcover format available at Costco (Item #1885238).