Lindsay Lohan -- First Shot Fired in Dubai War

TMZ has obtained the cease and desist letter Lindsay Lohan fired off to a Dubai-based party planning company ... demanding they stop using her name to promote a NYE party.

We broke the story ... Lindsay believes the company has been spreading lies about her ... falsely claiming she's agreed to attend a massive New Year's Eve bash on a gigantic ocean liner.

In the letter, Lohan's attorney, Stephanie Ovadia, states the actress "will suffer harm and damage" if the company continues to use her name without permission ... and she's not afraid to sue.