| John L. O'Brien | |
| Office: | 31st and 38th Speaker of the Washington House of Representatives |
| Term Start: | January 22, 1976 |
| Term End: | January 10, 1977 Acting |
| Predecessor: | Leonard A. Sawyer |
| Successor: | John A. Bagnariol |
| Term Start1: | January 10, 1955 |
| Term End1: | January 14, 1963 |
| Predecessor1: | R. Mort Frayn |
| Successor1: | William S. Day |
| Office2: | Speaker pro tempore of the Washington House of Representatives |
| Term Start2: | January 10, 1983 |
| Term End2: | January 11, 1993 |
| Predecessor2: | Otto Amen |
| Successor2: | Ron Meyers |
| Alongside3: | Otto Amen (1979–1981) |
| Term Start3: | January 8, 1973 |
| Term End3: | January 12, 1981 |
| Predecessor3: | Tom Copeland |
| Successor3: | Otto Amen |
| Office4: | Majority Leader of the Washington House of Representatives |
| Term Start4: | January 14, 1963 |
| Term End4: | January 9, 1967 |
| Predecessor4: | August P. Mardesich |
| Successor4: | Slade Gorton |
| Office5: | Minority Leader of the Washington House of Representatives |
| Term Start5: | January 9, 1967 |
| Term End5: | January 11, 1971 |
| Predecessor5: | Tom Copeland |
| Successor5: | Leonard A. Sawyer |
| Office6: | Member of the Washington House of Representatives |
| Constituency6: | 37th |
| Term Start6: | January 10, 1983 |
| Term End6: | January 11, 1993 |
| Predecessor6: | John Eng |
| Successor6: | Jesse Wineberry |
| Constituency7: | 35th |
| Term Start7: | January 8, 1973 |
| Term End7: | January 10, 1983 |
| Predecessor7: | John A. Bagnariol |
| Successor7: | Doug Sayan |
| Constituency8: | 33rd |
| Term Start8: | January 10, 1949 |
| Term End8: | January 8, 1973 |
| Predecessor8: | H. C. Armstrong |
| Successor8: | John E. Cunningham |
| Constituency9: | 33rd |
| Term Start9: | October 1, 1939 |
| Term End9: | January 13, 1947 |
| Predecessor9: | Harry D. Austin |
| Successor9: | H. C. Armstrong |
| Birth Name: | John Lawrence O'Brien |
| Birth Date: | 22 November 1911 |
| Birth Place: | Seattle, Washington, U.S. |
| Death Place: | Seattle, Washington, U.S. |
| Party: | Democratic |
| Occupation: | Accountant |
| Spouse: | Mary Schwarz |
| Children: | 6 |
| Alma Mater: | Saint Martin's University (BA) |
John Lawrence O'Brien (November 22, 1911 – April 22, 2007) was an American accountant and politician in the state of Washington. He served in the Washington House of Representatives from 1939 to 1947 and from 1949 to 1993.[1] [2]