As of 2015, Iran's largest ally is Russia, which it has strong diplomatic ties with; this has created a strong regional alliance. Iran is also allied with several other Islamic governments including Syria and the Palestinian Authority.
Iran has also formed diplomatic alliances with countries in Africa and South America. Venezuela and Iran announced a friendly alliance in 2007, including a $2 billion fund to invest in developing nations. Their stated goal was to help stop the spread of US imperialism in impoverished nations. Iran also has close ties with Sudan and Zimbabwe.
Syria is one of Iran's closest allies. The two nations have worked together since 1979, despite ideological differences. In 2014, they began working even more closely together due to the growing influence of the Islamic State (ISIS), a violent terrorist group.
Iran and Israel have a long history of opposition. Due to that and other factors, the Iranian government is allied with the Palestinian Authority and supports extremist Palestinian groups such as Hamas. However, Israel and Iran also share many political goals and have at times cooperated to reach their shared goals.
The threat posed by ISIS has led to a renewed strategic alliance between Iran and the United States. The two nations do not have a formal alliance, but both are working to stop ISIS, which has gained control of territory in both Iraq and Syria.