NiSource, Inc. is one of the largest fully regulated utility companies in the United States, serving approximately 3.5 million natural gas customers and 500,000 electric customers across seven states through its local Columbia Gas and NIPSCO brands. The company, based in Merrillville, Indiana, United States, has more than 7,000 employees.

NiSource's natural gas utilities provide domestically produced supplies of natural gas to residential, commercial and industrial customers via nearly 60,000 miles of pipeline and related facilities in seven states: Indiana, Kentucky, Maryland, Massachusetts, Ohio, Pennsylvania and Virginia.

NiSource provides electric energy to nearly 500,000 customers, all located in northern Indiana. NiSource’s electric operations include power generation, transmission and local distribution, as well as wholesale and electric transmission transactions. NiSource uses both traditional and renewable generation sources, including natural gas, hydroelectric, wind, and coal generated supplies, providing a total system operating net capability of more than 3,000 megawatts.

In 2015, NiSource was named to the Dow Jones Sustainability - North America Index for the second year in a row and for the ninth time since 1999.

NiSource operates seven local utilities in its service region.

On July 1, 2015, NiSource separated Columbia Pipeline Group (NYSE: CPGX) into a stand-alone publicly traded company. Each NiSource shareholder at the time of the separation received one share of Columbia Pipeline Group for each share of NiSource. The separation of Columbia Pipeline Group included Columbia Gas Transmission, Columbia Gulf Transmission, Columbia Midstream Group, its ownership in Columbia Pipeline Partners (NYSE: CPPL), and other natural gas pipeline, storage and midstream holdings.

In December 2011, the non-partisan organization Public Campaign criticized NiSource for spending $1.83 million on lobbying and not paying any taxes during 2008-2010, instead getting $227 million in tax rebates, despite making a profit of $1.4 billion, and increasing executive pay by 33% to $11.2 million in 2010 for its top 5 executives. One rule NiSource, among other companies, benefitted from was a bonus depreciation rule that lowered the federal tax expense. NiSource stated, “This law, enacted by Congress, encouraged companies like NiSource to accelerate capital investments to spur economic recovery by permitting portions of these investments to be deducted at an accelerated rate. Only the timing of the deductions was changed, and not the amount that could be deducted. This means our income tax expense will likely be higher in the future.”