The following railroads operate in the U.S. state of New Hampshire.
{{TOC right}}| Name | Mark | System[1] | From | To | Successor | Notes | | Ashuelot Railroad | B&M | 1844 | 1890 | Connecticut River Railroad |
| Atlantic and St. Lawrence Railroad | CN | 1847 | 1960 | Canadian National Railway |
| Berlin Mills Railway | BMS | | 1999 | St. Lawrence and Atlantic Railroad |
| Boston, Concord and Montreal Railroad | B&M | 1844 | 1890 | Concord and Montreal Railroad |
| Boston and Lowell Railroad | B&M | 1880 | 1919 | Boston and Maine Railroad |
| Boston and Maine Corporation | BM | B&M | 1963 | Still exists as a lessor of Pan Am Railways operating subsidiary Springfield Terminal Railway |
| Boston and Maine Railroad | B&M, BM | B&M | 1835 | 1964 | Boston and Maine Corporation |
| Brookline Railroad | B&M | 1891 | 1895 | Fitchburg Railroad |
| Brookline and Milford Railroad | B&M | 1893 | 1895 | Fitchburg Railroad |
| Canadian National Railway | CN | CN | 1923 | 1998 | St. Lawrence and Atlantic Railroad |
| Central Vermont Railroad | CN | 1873 | 1899 | Central Vermont Railway |
| Central Vermont Railway | CV | CN | 1899 | 1995 | New England Central Railroad |
| Cheshire Railroad | B&M | 1844 | 1890 | Fitchburg Railroad |
| Claremont and Concord Railway | CLCO | 1954 | 1988 | Claremont Concord Railroad |
| Cocheco Railroad | B&M | 1847 | 1863 | Dover and Winnipiseogee Railroad |
| Concord Railroad | B&M | 1835 | 1890 | Concord and Montreal Railroad |
| Concord and Claremont Railroad | B&M | 1873 | 1945 | Boston and Maine Railroad |
| Concord and Claremont Railroad | B&M | 1848 | 1853 | Merrimack and Connecticut River Railroad |
| Concord and Montreal Railroad | B&M | 1890 | 1919 | Boston and Maine Railroad |
| Concord and Portsmouth Railroad | B&M | 1855 | 1944 | Boston and Maine Railroad |
| Connecticut River Railroad | B&M | 1849 | 1919 | Boston and Maine Railroad |
| Contoocook River Railroad | B&M | 1856 | 1873 | Concord and Claremont Railroad |
| Contoocook Valley Railroad | B&M | 1848 | 1857 | Contoocook River Railroad |
| Dover and Winnipiseogee Railroad | B&M | 1862 | 1892 | Boston and Maine Railroad |
| Dover and Winnipisiogee Railroad | B&M | 1839 | 1841 | Boston and Maine Railroad |
| Eastern Railroad | B&M | 1839 | 1890 | Boston and Maine Railroad |
| Eastern Railroad in New Hampshire | B&M | 1836 | 1899 | Boston and Maine Railroad |
| Fitchburg Railroad | B&M | 1847 | 1919 | Boston and Maine Railroad |
| Franklin and Bristol Railroad | B&M | 1848 | 1849 | Northern Railroad |
| Franklin and Tilton Railroad | B&M | 1889 | 1943 | Boston and Maine Railroad |
| Glen Junction Transfer Company | 1897 | |
| Goodwin Railroad | GWIN | 1976 | 1981 | North Stratford Railroad |
| Grafton Railroad | B&M | 1847 | | Northern Railroad |
| Grand Trunk Railway | GT | CN | 1853 | 1923 | Canadian National Railway |
| Great Falls and Conway Railroad | B&M | 1844 | 1865 | Portsmouth, Great Falls and Conway Railroad |
| Groton and Nashua Railroad | B&M | 1844 | 1846 | Worcester and Nashua Railroad |
| Lake Shore Railroad | B&M | 1883 | 1901 | Concord and Montreal Railroad |
| Maine Central Railroad | MEC | MEC | 1888 | 2003 | New Hampshire Central Railroad |
| Manchester and Keene Railroad | B&M | 1864 | 1881 | Boston and Lowell Railroad/ Concord Railroad |
| Manchester and Lawrence Railroad | B&M | 1847 | 1919 | Boston and Maine Railroad |
| Manchester and North Weare Railroad | B&M | 1858 | 1899 | Concord and Montreal Railroad |
| Merrimack and Connecticut River Railroad | B&M | 1853 | 1873 | Concord and Claremont Railroad |
| Monadnock Railroad | B&M | 1848 | 1892 | Fitchburg Railroad |
| Nashua and Acton Railroad | B&M | 1907 | 1925 | N/A |
| Nashua, Acton and Boston Railroad | B&M | 1872 | 1906 | Nashua and Acton Railroad |
| Nashua and Epping Railroad | B&M | 1848 | 1868 | Nashua and Rochester Railroad |
| Nashua and Lowell Railroad | B&M | 1835 | 1944 | Boston and Maine Railroad |
| Nashua and Rochester Railroad | B&M | 1868 | 1883 | Worcester, Nashua and Rochester Railroad |
| New Boston Railroad | B&M | 1891 | 1934 | N/A |
| New Hampshire Central Railroad | B&M | 1848 | 1853 | Merrimack and Connecticut River Railroad |
| New Hampshire and Vermont Railroad | NHVT | 1989 | 2000 | New Hampshire Central Railroad |
| North Stratford Railroad | NSRC | 1977 | 1989 | New Hampshire Central Railroad |
| Northern Railroad | B&M | 1844 | |
| Pemigewasset Valley Railroad | B&M | 1874 | 1947 | Boston and Maine Railroad |
| Peterborough Railroad | B&M | 1866 | 1944 | Boston and Maine Railroad |
| Peterborough and Hillsborough Railroad | B&M | 1869 | 1945 | Boston and Maine Railroad |
| Peterborough and Shirley Railroad | B&M | 1846 | 1860 | Fitchburg Railroad |
| Portland and Ogdensburg Railroad | MEC | 1869 | 1887 | Portland and Ogdensburg Railway |
| Portland and Ogdensburg Railway | MEC | 1886 | 1943 | Maine Central Railroad |
| Portland, White Mountains and Ogdensburg Railroad | MEC | 1867 | 1869 | Portland and Ogdensburg Railroad |
| Portsmouth and Concord Railroad | B&M | 1845 | 1857 | Concord and Portsmouth Railroad |
| Portsmouth and Dover Railroad | B&M | 1866 | 1900 | Boston and Maine Railroad |
| Portsmouth, Great Falls and Conway Railroad | B&M | 1865 | 1890 | Boston and Maine Railroad |
| Portsmouth, New Market and Concord Railroad | B&M | 1845 | 1845 | Portsmouth and Concord Railroad |
| Portsmouth, New Market and Exeter Railroad | B&M | 1845 | 1845 | Portsmouth and Concord Railroad |
| Portland and Rochester Railroad | B&M | 1866 | 1900 | Boston and Maine Railroad |
| Profile and Franconia Notch Railroad | B&M | 1878 | 1901 | Concord and Montreal Railroad |
| Sugar River Railroad | B&M | 1866 | 1873 | Concord and Claremont Railroad |
| Sullivan Railroad | B&M | 1846 | 1866 | Sullivan County Railroad |
| Sullivan County Railroad | SC | B&M | 1866 | 1949 | Boston and Maine Railroad |
| Suncook Valley Railroad | B&M | 1870 | 1952 | N/A | Became independent from B&M in 1924. |
| Suncook Valley Extension Railroad | B&M | 1889 | 1947 | Concord and Montreal Railroad | Acquired by Suncook Valley Railroad in 1925. |
| Tilton and Belmont Railroad | B&M | 1883 | 1901 | Concord and Montreal Railroad |
| Twin State Railroad | TSRD | 1984 | 1999 | New Hampshire Central Railroad |
| Upper Coos Railroad | MEC | 1883 | 1982 | Maine Central Railroad |
| Vermont Central Railroad | CN | 1871 | 1873 | Central Vermont Railroad |
| West Amesbury Branch Railroad | B&M | 1868 | 1893 | Boston and Maine Railroad |
| White Mountains Railroad | B&M | 1848 | 1873 | Boston, Concord and Montreal Railroad |
| Whitefield and Jefferson Railroad | B&M | 1878 | 1904 | Concord and Montreal Railroad |
| Wilton Railroad | B&M | 1844 | 1944 | Boston and Maine Railroad |
| Wolfeboro Railroad | WLFB | 1975 | 1976 | Goodwin Railroad |
| Wolfeborough Railroad | B&M | 1862 | 1892 | Boston and Maine Railroad |
| Worcester and Nashua Railroad | B&M | 1845 | 1883 | Worcester, Nashua and Rochester Railroad |
| Worcester, Nashua and Rochester Railroad | B&M | 1883 | 1911 | Boston and Maine Railroad |
1. ^This is one or more of the Class I railroads that the railroad became part of, if any.