Sculptor Arturo Di Modica is really pissed about the location of "Fearless Girl" and fired off a pretty threatening letter to Mayor Bill de Blasio. In the letter, obtained by TMZ, he says he was never consulted about the new art piece, despite the fact it's clearly capitalizing on its proximity to the 'Bull.'

He believes she was made out of bronze to make her seem like she's packaged with the 'Bull.' Arturo's not down with that because he says it now seems like his 'Bull' is attacking a child.

Furthermore, Arturo notes the people behind 'FG' know they're taking advantage of his art piece because their original promotion said where she was placed "made her impossible to ignore."

He wants her immediately moved and he wants the city to pay him an undetermined amount in damages. Arturo says he wants to settle this amicably, but we smell lawsuit.

As for Bill de Blasio -- he's making it clear he stands behind "Fearless Girl." And that's no bull.