The natural gas field, named Eram, is located near the Persian Gulf in the southwestern province of Fars and holds about 19 trillion cubic feet of gas.
The discovery comes at an opportune time for Iran, which has suffered economically under a series of US sanctions.
"America cannot cease Iran's oil production. Sanctions have not stopped the Iranian oil industry. We are active. We are alive," Iranian Oil Minister Bijan Namdar Zanganeh said.