Sienna Miller lastly hooked up with a man out-of-wedlock ... in a good way.
The dude taking down Balthazar Getty's sloppy seconds is DJ Slinky Wizard -- who also goes by his birth name, George Baker.
The two did what Sienna does best while on vacation in Ibiza -- PDA.
No word if the Slinky Wizard turned any tricks while on the boat.
