Triangle

Blitz3D Forums/Blitz3D Beginners Area/Triangle

(I assume you mean 3d triangles?)
NO.
Have you even looked at the tutorials for B3D?

Look at Introduction to Meshes, in the 3d tutorial.

Although it gives you a square, its made up of two triangles.

And if you mean 2d, then no as well, but thats just drawing lines. And I would be very very supprised if there wasnt stuff in the code archives for drawing both filled and unfilled polygons