There are several free image optimization plugins available for WordPress. Some popular options include Smush, EWWW Image Optimizer, and ShortPixel.

Additionally, there are online image compression tools such as https://compress-or-die.com and TinyPNG that can be used to optimize images before uploading them to WordPress. These tools can help to reduce the file size of images without sacrificing quality, leading to faster load times and improved overall site performance.