The attacks, occurring from 2011 to 2013, are believed to have been co-ordinated from Iranian companies.
The US Department of Justice revealed an indictment against the seven, believed to be working for their government in Iran.
The indictment calls them "experienced computer hackers" and officials said the attacks were a "wake-up call".
It is the first time the US is charging people associated with a national government with hacking into US infrastructure for major industries like finance and water.
The attacks "threatened our economic well-being and our ability to compete fairly in the global marketplace - both of which are directly linked to our national security," said US Attorney General Loretta Lynch.
"And we believe that they were conducted with the sole purpose of undermining the targeted companies and damaging the online operation of America's free market."
Mrs Lynch said the attacks cost the victims tens of millions of dollars.
Ahmad Fathi, Hamid Firoozi, Amin Shokohi, Sadegh Ahmadzadegan, Omid Ghaffarinia, Sina Keissar and Nader Seidi are identified in the indictment as the alleged attackers.
The charges carry a maximum sentence of 10 years in prison for conspiracy to commit and aid and abet computer hacking.
It is almost certain that Iran will not send the accused to the US, and they have not been arrested.
The indictment is still important, said FBI director James Comey.
"The world is small, and our memories are long," he said. "We never say never. People often like to travel for vacation or education, and we want them looking over their shoulder."

Many of Paris's tourist attractions, including the Louvre and the Musee d'Orsay, closed on Saturday amid heightened security.
The institutions reopened at 13:00 local time following a minute's silence to honour those who were killed.
However the Eiffel Tower will remain closed until further notice.
A message on the tower's website added "the Eiffel Tower will not sparkle" on Monday night, during the period of national mourning, at the request of Paris Mayor Anne Hidalgo.
A total of 129 people died in the attacks by Islamist militants.
People were targeted in bars and restaurants, the Bataclan concert hall and the Stade de France.
In explaining the decision to reopen the venues, French Culture Minister Fleur Pellerin said although France had suffered a tragic event, "culture is more than ever this symbolic place of self-discovery".
Ms Pellerin added the government would help to boost security measures at public cultural institutions in Ile-de-France, the region immediately surrounding Paris.
Its landmarks include the Louvre, which houses Leonardo da Vinci's Mona Lisa painting, as well as the Eiffel Tower and the Notre Dame Cathedral.
Eighty-nine people died at the Bataclan venue, where US rock band Eagles of Death Metal had been performing.
Many concerts scheduled to take place in Paris over the weekend, including those by U2, Motorhead, Foo Fighters and Deftones, were also cancelled.
Cinemas were also ordered to close following Friday's attacks, but most reopened on Sunday.
The US has charged seven Iranians for allegedly hacking nearly 50 financial companies and a New York dam.
[NEXT_CONCEPT]
Public museums and other cultural venues in Paris have reopened following the attacks in the French capital on Friday.