The United States is expanding its sanctions against Iran because of concerns about its nuclear ambitions.
Washington said the individuals and institutions targeted were helping Iran to develop its nuclear programme.
This is the first step in implementing sanctions adopted by the UN Security Council last week.
Those blacklisted include Iran's Post Bank, Defence Minister Ahmad Vahidi and the air force and missile command of the Revolutionary Guard Corps.
Western powers accuse Iran of seeking to develop nuclear weapons - a charge Iran strongly denies.
Front companies targeted
The US sanctions prohibit any American business or individual from trading with those named on the blacklist. The sanctions also freeze any assets they may have under US jurisdiction.
"We will continue to target Iran's support for terrorist organisations, we will continue to focus on Iran's Revolutionary Guard, and we will continue to expose Iran's efforts to evade international sanctions," US Treasury Secretary Timothy Geithner told a White House news briefing.
Also on the list is a front company for the national shipping line, which is run by the Revolutionary Guards.
The Treasury has designated 27 new ships and has updated entries for 71 others whose names had been changed.
The designation of Post Bank brings to 16 the total number of Iranian banks under sanctions. The US Treasury says Post Bank is a front for Bank Sepah, which was designated in 2007 for providing financial services to the Iranian missile industry.
Last week, Iran's President Mahmoud Ahmadinejad dismissed the UN sanctions as "a used handkerchief" fit for the dustbin.
The European Union, which has been working closely with Washington, will decide on its own sanctions at a summit on Thursday.
The EU's proposed sanctions go further than the UN, targeting the oil and gas industry.
EU countries such as Germany and Italy have become important trading partners for Iran, but the EU is becoming increasingly concerned that Iran may be pursuing nuclear weapons.