DNA nanotechnology typically relies on Watson-Crick base pairing as both a recognition and structural element. This limits structural versatility and introduces errors during self-assembly of DNA. Guanine (G) quartet motifs show promise as an alternative to DNA duplexes, but the synthesis of long, precisely defined molecules is a significant challenge. Here we demonstrate a continuous tetrahelical DNA architecture capable of programmed self-assembly. We report that the homopolymer consisting of (G(3)T)(3)G(3) monomeric units has the capability to fold into a monomolecular DNA tetrahelix with unprecedented speed and stability. For instance, in the presence of 1 mM K+ ions the dimer, (G3T())2, folds readily and melts above 100 degrees C. These findings have the potential to revolutionize DNA nanotechnology by introducing fast and error-free self-assembly of long and extraordinarily stable molecules.