Forests around the world are under immense pressure from human land use and climate change. Old-growth and primary forests have been degraded in recent decades, yet are generally more resilient and resistant to climate change effects compared to human-modified forests. Nowhere is this more evident than in Russian Siberia, which contains almost one-fifth of the world's forest area and has been subjected to a variety of land uses and disturbances since the mid-20th century. Although a number of related geospatial products exist, there are no large-scale maps of old-growth and primary forests across Siberia. However, remotely sensed metrics of forest stability have been shown to relate to old-growth and primary forests in tropical and boreal environments. Here we apply stability indices from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors across boreal Siberia from 2003 to 2020. Our results indicate that forests in the central and southern taiga contain most areas of high stability, but also distinct zones of disturbance and low stability. We identified three regions with particularly low forest stability: (i) the Zabaikal region in southern Siberia, (ii) a portion of the central taiga spanning the Republic of Sakha (Yakutia), and (iii) the West Siberian lowlands. This approach can be used to monitor Siberian boreal forest condition, and could be applied to other boreal forested regions.