Top Alternatives to Terraria

Minecraft is sandbox world building game currently owned by Microsoft.

King Arthur's Gold is an online action video game for Windows, Mac and Linux.

Gnomescroll is an open source multiplayer voxel game.

Block Story combines popular 3D voxel, sandbox exploration gameplay with exciting and addictive role playing elements.

Mythruna (myth + rune + a) is a game under development attempting to combine serious role-playing elements with an endless, living, and completely modifiable randomly generated sandbox world.

Junk Jack is an action-adventure sandbox video game.

Voxelands is a free voxel world game.

Clonk is a single player and multiplayer computer game series.

Starbound is an action-adventure video game.

Cube World is an open world role-playing video game.

Growtopia is an experimental multiplayer creative sandbox game.