Comes from the sirloin section, which is on the back of a beef animal between the fore-rib and the rump.
The sirloin steak has great flavour and is suitable for grilling, pan-frying, griddling or cooking on a BBQ. To cook a 2cm/3-4 in thich steak:
Rare: 2½ minutes each side
Medium Rare: 3-3½ minutes each side
Medium: 4 minutes each side
Well done: 6 minutes each side
Leave to rest for a couple of minutes before serving.
If you're looking for something similar to a sirloin, try a rump steak which is taken from the rump muscle which is situated next to the sirloin.
Legend has it that sirloin is so called because it was knighted 'Sir Loin' by Henry VIII.