This is the highest figure since IHR began registering executions in Iran in 2008.
The organizations accuse Iran of using the death penalty as a "central tool for political oppression".
These executions are part of the Islamic Republic's war against its own people to maintain its grip on power, says IHR chief Mahmood Amiry-Moghaddam.
On average, five people were executed daily during the last three months of the year, when the threat of war between Iran and Israel escalated, he adds.
Of the 975 people executed, four people were hanged publicly. 31 were women, which is also the highest figure in the last 17 years.
So far this year, Iran has carried out at least 121 executions, according to IHR.
