Cincinnati Bell is the dominant telephone company for Cincinnati, Ohio, its nearby suburbs, and the Dayton metropolitan area in the U.S. states of Ohio, Indiana and Kentucky. The parent company is named Cincinnati Bell Inc. Its incumbent local exchange carrier subsidiary uses the name Cincinnati Bell Telephone Company LLC. Other subsidiaries handle services such as payphones and long distance calling. Since the 2000s, Cincinnati Bell has diversified into other utilities, such as IPTV and household electricity, while divesting its mobile phone subsidiary. Cincinnati Bell holds the naming rights to Cincinnati's streetcar system, the Cincinnati Bell Connector.

Cincinnati Bell started out as the City and Suburban Telegraph Association and was providing telegraph lines between homes and businesses in 1873, three years before the invention of the telephone. In 1878, it gained exclusive rights to the Bell franchise within a 25-mile (40-km) radius of Cincinnati—the first telephone exchange in Ohio. It has substantially the same incumbent local exchange carrier territory today, straddling 2,400 square miles in three states. The name changed to Cincinnati and Suburban Bell Telephone Company in 1903. It was shortened to Cincinnati Bell in 1971.

Cincinnati Bell and Southern New England Telephone (SNET) were the only two companies in the old Bell System that operated independently because AT&T Corporation only owned minority stakes in the companies. Therefore, neither is considered a Regional Bell Operating Company (RBOC), AT&T was not obligated to dispose of their ownership stakes in the companies, and restrictions placed on the Baby Bells did not apply to these two companies. AT&T owned 32.6% of Cincinnati Bell until 1984, at which point the shares AT&T owned were placed into a trust and then sold. In 1998, SNET was bought by SBC Communications (Now the new AT&T), an RBOC, and in 2014 was sold to Frontier Communications, a company with no relation to the former Bell System; however, Cincinnati Bell has remained independent.

The newsmagazine 60 Minutes reported in 1989 that Cincinnati Bell cooperated with local police to wiretap local residents in search of alleged communist or criminal activity from 1972 to 1984. In a move widely criticized by consumer advocates, Cincinnati Bell was also the first phone company in Ohio to take advantage of a 2005 state law that lets phone companies raise rates without having to gain approval from state regulators.

In May 1999, the Public Utilities Commission of Ohio awarded Cincinnati Bell Long Distance the right to offer local wireline telephone service in 55 counties outside its incumbent territory and began to resell business local phone service in these counties, in competition with incumbent carrier Ameritech.

During the 1990s, Cincinnati Bell acquired a nationwide transmission network formerly known as IXC Communications and changed its corporate name to "Broadwing Communications," although the local telephone operations continued to operate under their traditional name. In 2004, the holding company divested the long-distance operation as Broadwing Corporation and changed its name back to Cincinnati Bell.

In 2002, Cincinnati Bell sold Cincinnati Bell Directory, consisting of its directory operations, to Spectrum Equity. The resulting company is named CBD Media. The sale marked the first time a former Bell System-affiliated company sold off its directory operations.

In 2003, when BellSouth exited the payphone market, some former BellSouth payphones in Kentucky were sold to Cincinnati Bell.

Cincinnati Bell is the only American Bell System company that continues to publicly do business under the "Bell" name. In July 2006, Cincinnati Bell removed the final Bell logo—designed in 1969 by Saul Bass—from most of its corporate branding, leaving only a stylized wordmark. However, the company continued to use the Bell logo in promotional materials for residential landline and long-distance service until another it adopted a new logo in 2016. (BellSouth was the last remaining Baby Bell to still use the Bell logo, but BellSouth was acquired by AT&T later that year, with the BellSouth brand being retired in 2007.)

Cincinnati Bell's original headquarters, the Cincinnati and Suburban Telephone Company Building, is listed on the National Register of Historic Places.

On July 10, 2017, Cincinnati Bell announced it would acquire Hawaiian Telcom Holdco, Inc., parent of local telephone company Hawaiian Telcom for $650 million and Toronto-based OnX Enterprise Solutions for $201 million.

Cincinnati Bell provides landline PSTN local and long-distance calling. In recent years, the company has seen subscriptions to these traditional services decline due to competition from cable and wireless providers.

From 1998 until 2015, Cincinnati Bell Wireless (CBW) offered GSM wireless service in southeastern Indiana, southwestern Ohio, and northwestern Kentucky. It was sold at Best Buy, Circuit City (until 2009), Office Depot, and participating Kroger locations. It offered HSPA+ service in most of Hamilton County, Ohio, and parts of surrounding counties; EDGE service in Dayton and Oxford; and GSM service elsewhere. The local coverage area extended north to Celina and Urbana, east to Hillsboro, south to Corinth and Warsaw, and west to Batesville. Cincinnati Bell's prepaid mobile phone products were sold under same i-wireless brand as an unrelated service by locally based Kroger.

Cincinnati Bell made its first foray into wireless telephony around 1986, when it acquired a 45% stake in Ameritech Cellular. On February 2, 1998, Cincinnati Bell acquired 80% of AT&T Wireless Services's new Cincinnati-Dayton PCS network for over $100 million. Cincinnati Bell's subsidiary Cincinnati Bell Wireless was responsible for marketing and sales, while AT&T Wireless handled technical operations for the joint venture. Wireless service began by June in Cincinnati and by September in Dayton, eventually covering a 21-county area. When AT&T Wireless was purchased by Cingular, now known as AT&T Mobility, control of its 20% stake also passed to Cingular. On February 17, 2006, Cincinnati Bell took full control of CBW by purchasing Cingular's stake for $83 million. As a part of the deal, Cincinnati Bell and Cingular secured lower roaming charges on each other's respective GSM networks.

An independent research provider tested Cincinnati Bell Wireless's service in Cincinnati and Dayton and found the company to have the best wireless network in 2005 and 2006. Cincinnati Bell Wireless had 571,000 wireless subscribers at the end of 2007 and 196,000 postpaid wireless subscribers at the end of 2013.

On April 7, 2014, Cincinnati Bell announced plans to sell its wireless spectrum and other assets to Verizon Wireless, as part of a planned emphasis on enterprise and entertainment services such as FiOptics. Cincinnati Bell Wireless ended service on February 28, 2015. The company's retail locations began selling Verizon products.

Cincinnati Bell offers Internet access to customers in its service area. Cincinnati Bell's Fuse Internet Service provides dial-up access, while its broadband access is through its ZoomTown ADSL service. ZoomTown customers still connect to the Internet through an Internet service provider. Typically, ZoomTown is used in conjunction with Cincinnati Bell's ISP, Fuse, although other local ISPs are available. ZoomTown's ADSL technology currently offers three speeds of 5 Mbit/s and 768 kbit/s downstream. ZoomTown started service in 1999. Cincinnati Bell also offers a service called ZoomTown Plus that bundles Internet access with news, reference, and entertainment content, provided though Synacor. Cincinnati Bell has started offering Zoomtown Internet at speeds from 5 Mbit/s up to 1 Gbit/s in conjunction with its FiOptics services. The availability is limited to areas currently wired for FiOptics, and other FiOptics services are not required. In areas now covered by FiOptics, Cincinnati Bell no longer offers ADSL-only speeds of greater than 5 Mbit/s.

Its primary competitor for broadband Internet access is Charter Spectrum Internet.

In late 2009, Cincinnati Bell started offering a fiber-optic communications (Internet, telephone, and IPTV) service called FiOptics, similar to the U-verse service offered by AT&T and the FiOS service offered by Verizon Communications. Cincinnati Bell is currently in the process of rolling out the new service to select communities in the Cincinnati area. FiOptics runs fiber to the home, augmented by fiber to the node. In August 2014, Cincinnati Bell began offering gigabit Internet speeds with its FiOptics service.

In 2011, Cincinnati Bell became the first telecommunications company to also provide retail energy service. Through a partnership with Viridian Energy, Cincinnati Bell Energy competes with several other alternative electricity retailers for the power generation portion of customers' electricity bills. The subsidiary advertises that its service is entirely sourced from regional wind power certified by Green-e Energy.

Cincinnati Bell originally operated a chain of Cincinnati Bell Phone Center locations until 1992, when it sold the retail chain to AT&T. It reentered the retail space in 1998 with three Store@Cincinnati Bell retail locations. As of 2015, the company operates eight Cincinnati Bell Stores.

– Still in operation, but no longer offers cable or Internet as part of its services