The adsorption of a submonolayer of catechol (C<sub>6</sub>H<sub>6</sub>O<sub>2</sub>) on the rutile TiO<sub>2</sub>(110)-1×1 surface has been investigated by Scanning Tunneling Microscopy (STM). The catechol molecules are preferentially adsorbed on the surface 5-fold coordinated Ti<sup>4+</sup> sites, and occupy two neighboring lattice Ti sites. No preference for adsorption at surface step edges is observed at room temperature. A statistical analysis of intermolecular distances demonstrates that the interaction between the molecules strongly depends on the surface crystallographic direction: catechol molecules exhibit attractive interaction along [1-1 0], while they repel each other along the  direction. The attractive interaction is proposed to be caused by the coupling of π bonding electrons and the repulsive interaction is possibly mediated by substrate.