Context :

Aims : X-ray emission is an important diagnostics to study magnetic activity in very low mass stars that are presumably fully convective and have an effectively neutral photosphere .

Methods : We investigate an archival XMM-Newton observation of LHS 2065 , an ultracool dwarf with spectral type M9 .

Results : We clearly detect LHS 2065 at soft X-ray energies in less than 1 h effective exposure time above the 3 \sigma level with the PN and MOS1 detector .
No flare signatures are present and we attribute the X-ray detection to quasi-quiescent activity .
From the PN data we derived an X-ray luminosity of L _ { X } = 2.2 \pm 0.7 \times 10 ^ { 26 } erg/s in the 0.3 –0.8 keV band , the corresponding activity level of log L _ { X } / L _ { bol } \approx - 3.7 points to a rather active star .
Indications for minor variability and possible accompanying spectral changes are present , however the short exposure time and poor data quality prevents a more detailed analysis .

Conclusions : LHS 2065 is one of the coolest and least massive stars that emits X-rays at detectable levels in quasi-quiescence , implying the existence of a corona .