The following elections occurred in the year 1878.
Europe
United Kingdom
- 1878 Argyllshire by-election
- 1878 Belfast by-election
- 1878 Boston by-election
- 1878 Bristol by-election
- 1878 Canterbury by-election
- 1878 Carmarthen Boroughs by-election
- 1878 Cirencester by-election
- 1878 Down by-election
- 1878 East Somerset by-election
- 1878 Flint Boroughs by-election
- 1878 Greenock by-election
- 1878 Haddington Burghs by-election
- 1878 Hereford by-election
- 1878 Leith Burghs by-election
- 1878 Londonderry County by-election
- 1878 Maldon by-election
- 1878 Marlborough by-election
- 1878 Mid Somerset by-election
- 1878 Middlesbrough by-election
- 1878 Middlesex by-election
- 1878 New Ross by-election
- 1878 Newcastle-under-Lyme by-election
- 1878 North Lancashire by-election
- 1878 North Staffordshire by-election
- 1878 Oxford University by-election
- 1878 Oxfordshire by-election
- 1878 Perth by-election
- 1878 Perthshire by-election
- 1878 Peterborough by-election
- 1878 Reading by-election
- 1878 Rochester by-election
- 1878 South Northumberland by-election
- 1878 Southampton by-election
- 1878 Tamworth by-election
- 1878 Truro by-election
- 1878 West Kent by-election
- 1878 Worcester by-election
- 1878 York by-election
Rest of Europe
North America
Canada
- 1878 British Columbia general election
- 1878 Canadian federal election and 12 By-elections to the 4th Canadian Parliament
- 1878 Manitoba general election
- 1878 New Brunswick general election
- 1878 Newfoundland general election
- 1878 Nova Scotia general election
- 1878 Quebec general election
United States
- United States House of Representatives elections in California, 1878
- 1878 New York state election
- United States House of Representatives elections in South Carolina, 1878
- 1878 South Carolina gubernatorial election
- 1878 and 1879 United States House of Representatives elections
- 1878 and 1879 United States Senate elections