Context : Since its launch , the X-ray and \gamma -ray observatory INTEGRAL satellite has revealed a new class of high-mass X-ray binaries ( HMXB ) displaying fast flares and hosting supergiant companion stars .
Optical and infrared ( OIR ) observations in a multi-wavelength context are essential to understand the nature and evolution of these newly discovered celestial objects .

Aims : The goal of this multiwavelength study ( from ultraviolet to infrared ) is to characterise the properties of IGRÂ J16465 - 4507 , to confirm its HMXB nature and that it hosts a supergiant star .

Methods : We analysed all OIR , photometric and spectroscopic observations taken on this source , carried out at ESO facilities .

Results : Using spectroscopic data , we constrained the spectral type of the companion star between B0.5 and B1 Ib , settling the debate on the true nature of this source .
We measured a high rotation velocity of v = 320 \pm 8 \ > \mathrm { km } \mathrm { s } ^ { -1 } from fitting absorption and emission lines in a stellar spectral model .
We then built a spectral energy distribution from photometric observations to evaluate the origin of the different components radiating at each energy range .

Conclusions : We finally show that , having accurately determined the spectral type of the early-B supergiant in IGRÂ J16465 - 4507 , we firmly support its classification as an intermediate supergiant fast X-ray transient ( SFXT ) .