We've rounded up 20 of our favorite websites where you can download free 3D printing STL files to print on your own 3D printers.

While some of these listed below also offer STL files to purchase from the designers who created them, there are thousands of free files available all over the internet from the amazing open-source community.

Check out these sites below to find some new fun projects to 3D print on your own machines.

NASA has a wonderful page full of 3D Models and STL treasures for those of you who are interested in 3D printing objects from our history in space!

While NASA's site doesn't offer the most STL files available out there, you can however, find models to 3D print your own Apollo 11 landing site, the Hubble Space Telescope, the Curiosity Rover, models of spacesuits and rockets, asteroids and even the "Made in Space" space wrench!

Tinkercad is one of the best educational focused websites out there, with free STL files created from it's users, fantastic resources for teachers and students, design challenges and lesson plans.

Tinkercad is a free web app for 3D design, electronics, and coding. This is the ideal introduction to Autodesk, a global leader in design and make technology.

The NIH (National Institute of Health)United States government agency for biomedical and public health research has collected and offers free scientifically accurate or medically applicable STL files to 3D print.

The STL file collections include a variety of human organs and body parts to 3D print for research. They also include 3D printable medical equipment like face shields and low-cost prosthetics.

You can also 3D print models of DNA and viruses if you are interested in seeing these fascinating complex microscopic objects.

If you are looking for a fun project to do for yourself or with students of all ages, you may want to check out the e-NABLE Community, a group of thousands of volunteers from all over the world who are creating free 3D printed hands and arms for those in need.

There are multiple open-source 3D printable files to make a variety of sizes and designs for functional hand devices that you can print out for fun or donate to the community to provide a hand for someone who could use it.

This is an incredible service learning project for students of all ages where they get to solve real world problems with 3D printing technology.

Join thousands of schools and volunteers in making a difference with 3D printing!

The Smithsonian Institute is the largest museum, education, and research organization in the world. It hosts more than 142 million exhibits with more than 9,500 of them having been 3D scanned and made available to the public. Over 3,000 of these are now 3D printable!

African Fossils is a website focused on educating people on prehistoric topics using 3D printing. More than 180 high-quality fossils have been 3D scanned to share with the public. The files are often used by scientists, students and those who are just plain interested in learning more about fossils.

This website categorizes the scans into categories like hominids, animals, and tools and also allows their users to filter searches by fossil age. If you or your students would like to 3D print accurate human skulls through the ages this is the place for you!

Toymakr3D is a website by an Indonesian company selling toy models you can 3D print. Many of the models are free to download and print. The 3D printed designs are very detailed and wonderfully articulated, so your robots and creatures can move around easily and hold a variety of cool poses which makes them fantastic for creating stop-motion animations.

Customize and create. your own accessories for your bots and beasts or use the files as a starting point to create your very own unique creation!

Instructables is an incredible open-source community website where users can share their projects of all types. Many of these projects include things created with 3D printers. Instructables is a pro at offering the tutorials and instructions on how to build each design and project as well as offering the 3D printer files to download.

Many of the designers are very active on the website and are fantastic about answering your questions if you should find yourself wondering about anything related to their project that they shared.