Single-crystalline barium titanate nanowires are synthesized using a solution-based method, and their ferroelectric properties are investigated by scanning probe microscopy. Pristine nanowires have diameters ranging from 5 to 70 nm and lengths exceeding 10 mum, and they possess perovskite structures with a principal axis aligned along the wire axis. Scanning-probe microscopy investigations show that local non-volatile electric polarization can be reproducibly induced and manipulated on nano wires as small as 10 nm in diameter.