GoKawiilBT Group is best known today for broadband, mobile service and the infrastructure running underneath much of the UK's communications network. Its history, however, starts long before the telephone was a household fixture. BT's lineage reaches back to the Electric Telegraph Company, founded by William Fothergill Cooke and businessman John Lewis Ricardo in 1846 to commercialize electric telegraph technology developed by Cooke and Charles Wheatstone.
The Electric Telegraph Company merged with the International Telegraph Company in 1855, forming the Electric and International Telegraph Company, before being taken over by the General Post Office in 1870. So BT's claim to 1846 comes through its family tree, rather than one company somehow surviving intact for nearly two centuries.
BT isn't the only telecom company with an impressive pedigree, either. Sweden's Telia traces its roots to a state telegraph agency founded in 1853, Telecom Egypt points to its first telegraph line in 1854 and Norway's Telenor dates its beginnings to the Norwegian Telegraph Administration in 1855.
France can go further still, with a state-run optical telegraph network dating to 1794. The catch is that none of these are perfect apples-to-apples comparisons. Like BT, their histories run through government agencies, reorganizations and later commercial companies, which makes crowning a single "world's oldest" telecom company considerably messier than comparing birthdays.