React's Official Documentation:
This is the best place to start. It's well-written, thorough, and contains explanations straight from the developers who built React.
freeCodeCamp:
This is a free resource that has a broad range of coding tutorials, including React.
Codecademy:
Codecademy offers a hands-on course on React. Some of the content is behind a paywall.
Scrimba:
Scrimba offers a unique platform where you can interact with the code directly in the tutorials.
Egghead has video lessons on React. Some of the content is behind a paywall.
Udemy:
Udemy has several comprehensive courses on React. Note that courses on Udemy cost money, but they often have sales.
Frontend Masters:
Frontend Masters has some great in-depth courses on React. This is a subscription service.
Frontend Masters — Learn JavaScript, React, Vue & Angular from Masters of Front-End Development!
Pluralsight:
Pluralsight also offers various courses on React. This is also a subscription service.
Online Courses, Learning Paths, and Certifications - Pluralsight
Coursera:
Several universities and companies provide courses on React.
edX:
Similar to Coursera, you can find courses from universities and companies on React.