What’s the difference? Is there a difference?
Traditionally, the French (Old World) call it Syrah, the Australians (New World) Shiraz. Although, this division has been blurred by globalism.
Going back to the early 1800’s, Australian grape growers imported Syrah grapes from France (growing in the Rhone Valley since the Roman period), planted them widely, and started calling them Shiraz.
It’s generally assumed that Syrah and Shiraz are the same grape—but growing in different soil and different climate, it’s believed to change a bit slightly by mutating in the past 200 years.
Some people believed that the name Shiraz developed by the accented pronunciation of Syrah. Others believe that the name change was a strategic move credited to differentiate the Australians from the French. You can come to your own conclusions.
And now, some California producers are calling their Syrah wines Shiraz, to hint to the consumer that their wine is made in the New World fruit-forward style. Generally, only the Australians call their wines Shiraz, but non-Australian producers are using the name to define the style, as well as its marketability.
Both Syrah and Shiraz are made in a wide range of styles, from fresh fruit and easy drinking, to highly concentrated and intense.
Syrah has a reputation as a drier, more restrained wine while Shiraz is thought to be jammier and fruitier.
Syrah’s are generally (slightly) leaner than the Aussie style, yet more complex (spice, cherry, leather, tar, smoke, cassis, plum, etc.), earthy, lively (more acidity), tannic, and typically capable of short to long-term bottle ageing.
Shiraz wines that are full bodied and rife with rich, ripe, and intense fruit flavours (plum, blackberry, cherry, jammy, etc.) and hints of spice, and generally a touch more alcohol. These fruit driven wines are usually made in an easy drinking style and are good everyday wines.
And recently, you can throw Petite Sirah into the mix to confuse people even more. Petite Sirah is not Syrah at all, but in most cases, a descendant of a minor Rhone grape called Durif. But when the two grapes became popular in California in the 1970s, many winemakers and consumers used the two names interchangeably. Until recently, with DNA testing, the two grapes properly understood to be separate varieties.
Note: The facts for this article were culled from a variety of sources.
Grape Stains by Jimmy 
Great little lesson, I did not know the difference i assumed it was just eleitists using different spelling.
Thanks for this concise explanation. After visiting Sydney and the Hunter Valley region on a casual day trip, I was curious about the overall story of the Shiraz grape. I appreciate your inclusion of the detail about Petite Syrah and also the way in which California vintners are intentionally using the name/style Shiraz to indicate the taste profile. Well presented!