Minecraft!

Minetest is a near-infinite-world block sandbox game and a game engine, inspired by InfiniMiner, Minecraft, and the like.

Terasology (started under the name Blockmania) is an open source project started by Benjamin “begla” Glatzel to research procedural terrain generation and efficient rendering techniques in Java using the LWJGL. The engine uses a block-based voxel-like approach as seen in Minecraft. After proving itself as a solid tech demo begla was joined at first by Anton “small-jeeper” Kireev and Rasmus “Cervator” Praestholm and a full-fledged game concept was born.

You are marooned on the shores of an infinite blocky world. Explore, mine resources, craft tools and weapons, hunt and make traps. Build a shelter to survive nights and share your worlds online. Possibilities are infinite in this sandbox survival and construction game.

Starbound is an indie game being produced by the UK-based independent game studio Chucklefish Ltd. Starbound takes place in a two-dimensional, procedurally generated universe which the player will explore in order to obtain new weapons, armor, and miscellaneous items. Starbound entered beta testing on December 4, 2013 for Microsoft Windows, OS X and Linux.

Creativerse is a sandbox adventure game set in a beautiful yet treacherous world shrouded in mystery. Adventure solo or bring your friends, unearth secrets, and tame the land together!

The Fun-Focused Free Software Voxel World Game.

In a galaxy of procedural worlds made entirely from LEGO bricks, will you...

Unturned is a sandbox game in the emerging multiplayer apocalypse survival genre. Rather than focusing on being an MMO it provides players with easy systems to sit down and survive the zombie infestation with their friends. Over the course of a typical adventure, groups will have a blast fortifying locations, scavenging for supplies, trying to live off the land and negotiating with other people.

Mythruna is a game under construction combining extensive world building, crafting, and sandbox elements with just a touch of role-playing. When completed, Mythruna will be a unique gaming experience.

Manic Digger is an open-source implementation of block-building games, like the famous game Minecraft.Manic Digger aims to be a generic platform ontop of which you can create your own game-types and scenarios. Through server-side scripting, almost any type of block-building game should be possible.

ROBLOX is an online virtual playground and workshop - where kids of all ages can safely interact, create, have fun, and learn.

Stonehearth is a game about exploration and survival in an epic fantasy setting. Your job is to help a small group of settlers survive and carve out a place for themselves in a hostile land. You’ll need to establish a food supply, build shelter, defend your people, and find a way to grow and expand, facing challenges at every step.

Night is falling and your blockhead is freezing. You haven't yet made shelter and your campfire has gone out. All you have is a spade, some wood and a few sticks. You have only minutes before exhaustion hits. Do you create a bed, dig a cave or refuel your fire?

Freeminer is a Minecraft-inspired sandbox game.