"The 9th Microquasar Workshop: Celebrating over 50 years of discovery" will be held in Cagliari (Sardinia), Italy, on 20-24 September 2021. Given the situation related to the COVID-19 pandemic, the conference has been postponed from September 2020 to 2021.

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 conference will be hybrid. It will take place at the Theater of the Palazzo Doglio, in the heart of Cagliari. The number of participants on-site is limited to 100, in order to fully respect the protective measures and social distancing. Precedence is given to people who have filled-in the pre-registration form. Note that some places for attending in presence are still available! A good technical service (including a cameraperson and a technician) will ensure a high quality for participants connected remotely, via Zoom. Note that Sardinia is a very popular tourist destination therefore we strongly recommend you book your flight and hotel as soon as possible.

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.

The scientific program will be organized in several sessions including invited reviews, contributed talks, posters and time for discussion, such as how to optimize multi-lambda campaigns and collaborations, diversity in science (status of young researchers, women, under-represented minorities and people from disadvantaged countries). A visit to the Sardinia Radio Telescope will be possibly planned. Along with the scientific program, cultural and social events will be organized (if possible).