We introduce Electro Pen Nanolithography (EPN), a nanoscale chemical patterning technique. In a single sweep of an ink-coated, biased conducting Atomic Force Microscope (AFM) probe-tip, an underlying thin organic film is oxidized, and the ink molecules are transferred directly to the oxidized regions. Results using trialkoxysilane inks with functional terminal groups are presented, where the same ink-covered tips are used to image the pattern with zero bias. This technique provides very fast-exceeding 10 mu m/s-writing speeds with line-widths as small as 50 nm. Controlled multi-write operations permit the growth of an integer number of molecular layers. Multiple chemical patterns using a single probe-tip are demonstrated.