We present photometry and moderate-resolution spectroscopy of the luminous red variable [ HBS2006 ] 40671 originally detected as a possible nova in the galaxy M 33 .
We found that the star is a pulsating Mira-type variable with a long period of 665 days and an amplitude exceeding 7 mag in R band .
[ HBS2006 ] 40671 is the first confirmed Mira-type star in M 33 .
It is one of the most luminous Mira-type variables .
In the K band its mean absolute magnitude is M _ { K } = - 9.5 , its bolometric magnitude measured in the maximum light is also extreme , M _ { bol } = - 7.4 .
The spectral type of the star in the maximum is M2e - M3e .
The heliocentric radial velocity of the star is -475 km/s .
There is a big negative excess ( - 210 km/s ) in radial velocity of [ HBS2006 ] 40671 relative to the average radial velocity of stars in its neighborhood pointing at an exceptional peculiar motion of the star .
All the extreme properties of the new Mira star make it important for further studies .