The activity-rotation relation of M dwarfs provides observational evidence of the stellar dynamo, which is poorly understood for fully convective stars. It is known that the X-ray activity-rotation relation has a two-regime behavior with saturation for faster rotating stars and with a Lx decrease for slower rotation. However, the number of M dwarfs with sensitive X-ray and rotation measure- ments has for a long time been very limited. New XMM-Newton, Chandra and eROSITA X-ray observations with K2 mission and TESS rotation periods analyzed in my work have substantially increased the number of low activity and fast/slow rotation stars that have been dicult to assess in the past. Combining the new data with a systematic update and homogenization of the literature data has enabled me to examine the activity-rotation relation in different mass bins within the M dwarf regime. Several interesting findings emerged, including a non-constant Lx-level in the saturated regime and a mass-dependence of the slope in the unsaturated regime.

{"references": ["Magaudda et al. 2020, A&A, 638, A20", "Raetz et al. 2020, A&A, 637, A22", "Reiners et al. 2015, ApJ, 794"]}