The average price for a gallon of gasoline jumped 11 cents overnight to about $3.11 in the U.S., according to motor club AAA.
Gas prices were already rising before the U.S. launched strikes on Iran as refiners switch over to summer blends of fuel, but crude futures have risen sharply this week because of the war.
On Tuesday, oil futures soared to levels not seen in more than a year as Iran launched a series of retaliatory attacks, including a drone strike on the U.S. Embassy in Saudi Arabia.
Iran has also struck energy facilities in Qatar and Saudi Arabia, and disrupted tanker traffic through the Strait of Hormuz, the narrow mouth of the Persian Gulf through which a fifth of all oil traded passes, sending global oil and natural gas prices soaring.
Benchmark U.S. crude jumped 8.6% to $77.36 a barrel.
Brent crude, the international standard, added 6.7% to $81.29 a barrel. Global oil prices jumped to start the week over concerns that the war will clog the global flow of crude.
The price of crude is the single largest factor in how much U.S. drivers pay for fuel. And higher oil prices are usually felt at the pump within a couple of weeks at most.
Crude price increases are substantially reflected in pump prices in 20 days and a $10 per barrel increase typically results in a rise of around 25 cents per gallon, according to 2019 research by the Federal Reserve Bank of Dallas.
The Associated Press contributed to this report.