"The 9th Microquasar Workshop: Celebrating over 50 years of discovery" will be held in Cagliari (Sardinia), Italy, on 21-25 September 2020. It is the ninth in a series of conferences mainly devoted to microquasars but also covering relativistic jet sources in a broader context. It will also be an occasion to celebrate the 50 years since the discovery of variable radio emission from X-ray binaries. The workshop aims to present and discuss the latest results related to X-ray binaries, in particular accretion/ejection physics (multi-wavelength observations and theory/simulations), the properties, mechanisms and interplays of the accretion disk, disk winds, jets, accretion/ejection at all scales, and comparison with the various accretions (BH, NS, CV). The formation, evolution and merging of compact objects in binaries will also be addressed. In the context of recent missions devoted to transient sources, new facilities will be discussed (such as NICER, HXMT, MeerKAT, ASKAP, etc), in addition to new tools and diagnostics based on X-ray timing.