Mucha

Of course. BTW, his last name is pronounced more like "mu'ha" than "much-ah". Ch is pronounced like x in Quixote.

"Alfons Maria Mucha (1860 – 1939), known in English as Alphonse Mucha, was a Czech  Art Nouveau painter and decorative artist, known best for his distinct style. He produced many paintings, illustrations, advertisements, postcards, and designs."

Doesn't say much, does it?

Frankly, you will soon know your Mucha, just make a search on the internet... I love his ornaments, colors, lines, beautiful ladies, of course, like most others, but as an illustrator, I'm more impressed of his monumental nationalistic works... I had the fortune of see Mucha in an exhibition here in Stockholm a couple of years ago... his paintings are... *sigh* Things like that make a girl feel pretty modest :-D (In the "and I thought I had something going on in painting...")

People mention Eugene-Samuel Grasset as one of his influences. I'm pretty sure he was influenced by everything around him, just like everyone else, but Grasset isn't bad.

Other influences mentioned are Hans Makart

The Five Senses

Jules Joseph Lefebvre

 Truth

Pandora

Gustave Boulanger

I mean... *leer*

Jean Paul Laurens

Japanese woodcuts - the great wave of Japonisme that flushed over Europe in the end of the 19th century.

Here's a long list of different Art Nouveau poster artists and others, that might be of interest. There's a lot Muchaesque things there - it's difficult to know who influenced whom ;-)