Although the report is based on material that came from Ukrainian sources, Russia has blocked UN human rights investigators from gaining access to the peninsula.
The UN report cites "grave human rights violations, such as arbitrary arrests and detentions, enforced disappearances, ill-treatment and torture, and at least one extra-judicial execution".
It adds that there have been "intrusive law enforcement raids of private properties" which "interfered with [the] right to privacy".
The report, which says the human rights situation has "significantly deteriorated" in the region, notes that hundreds of prisoners were illegally transferred from Crimea to Russian jails.
It says civil servants were forced to renounce their Ukrainian citizenship or face losing their jobs, and condemned Moscow's decision to replace Ukrainian laws with Russian ones.
"Education in Ukrainian has all but disappeared from Crimean schools," the report adds.
It is based on interviews conducted from mainland Ukraine, as human rights investigators were not permitted entry into the region.