The country's biggest non-metropolitan district council, by population, has come into being after a merger.
East Suffolk, made up of the former Suffolk Coastal and Waveney district councils, will serve 246,913 people.
A second new authority, West Suffolk, has taken over from St Edmundsbury and Forest Heath councils.
West Suffolk will serve a population of 179,248 and the number of councillors to be elected for both new authorities in May will be reduced.
The mergers have taken two years of negotiating and will have fewer elected representatives with East Suffolk cutting the number of councillors from 90 to 55, and West Suffolk from 72 to 64.
Suffolk Coastal and Waveney have been working in partnership since 2008, sharing an "integrated workforce" and, on its website, East Suffolk council said the two separate councils had saved £16m since 2010.
Dr Christopher Huggins, politics lecturer at the University of Suffolk said at a time when local authorities have less money from central government and an increased demand for services, the major driver behind this decision has been to be more financially efficient.
"One of the risks of creating bigger councils is that you start to remove local representation from people."
Dr Huggins added the evidence of success of other so-called "super councils" remained "mixed".
Biggest non-metropolitan district councils by population
- East Suffolk 246,913
- Northampton 225,656
- Aylesbury Vale 196,020
- Basildon 184,479
- Charnwood 180,387
Source: University of Suffolk
Andy Storer, runs the Black Dog deli in Walberswick in the former Suffolk Coastal district, and he will now be represented by East Suffolk Council.
He said "everything seems to work smoothly in Suffolk" but he was in favour of anything which "reduces bureaucracy".
"But if it's about saving money then it's not putting the citizens first. That's the most important thing about it."
Suffolk has a two-tier system - with the top tier being the county council which provides services such as highways maintenance, schools, social services and libraries.
The second tier now has five district councils instead of seven which are responsible for services such as refuse collections, housing, planning permission and parks and leisure.
East Suffolk's chief executive Stephen Baker said: "This is a momentous day... and yet it will very much be business as usual."
Chief executive at West Suffolk, Ian Gallin, echoed those sentiments adding people "should see no difference in the day-to-day way they engage with us, but the new council will mean we are better able to champion West Suffolk and face the challenges ahead."