The 129th Maine Senate had 35 members each elected to two-year terms in November 2018. The first regular session was sworn in on December 5, 2018.
The 129th Senate party composition was:
| Position | Name | Party | Residence | County | |
|---|---|---|---|---|---|
| Aroostook | |||||
| Androscoggin | |||||
| Assistant Majority Leader | Democratic | Sagadahoc | |||
| Dana Dow | Republican | Waterboro | Lincoln | ||
| Assistant Minority Leader | Androscoggin |
| District | Senator | Party | Municipality | County | |
|---|---|---|---|---|---|
| 1 | Troy Jackson | Democratic | Allagash | Aroostook | |
| 2 | Michael E. Carpenter | Democratic | Houlton | Aroostook | |
| 3 | Bradlee Farrin | Republican | Norridgewock | Somerset | |
| 4 | Paul T. Davis | Republican | Sangerville | Piscataquis | |
| 5 | James Dill | Democratic | Old Town | Penobscot | |
| 6 | Marianne Moore | Republican | Calais | Washington | |
| 7 | Louis Luchini | Democratic | Ellsworth | Hancock | |
| 8 | Kimberly Rosen | Republican | Bucksport | Hancock | |
| 9 | Geoffrey Gratwick | Democratic | Bangor | Penobscot | |
| 10 | Stacey Guerin | Republican | Glenburn | Penobscot | |
| 11 | Erin Herbig | Democratic | Winterport | Waldo | |
| 12 | David Miramant | Democratic | Camden | Knox | |
| 13 | Dana Dow | Republican | Waterboro | Lincoln | |
| 14 | Shenna Bellows | Democratic | Manchester | Kennebec | |
| 15 | Matthew Pouliot | Republican | Augusta | Kennebec | |
| 16 | Scott Cyrway | Republican | Benton | Kennebec | |
| 17 | Russell Black | Republican | Wilton | Franklin | |
| 18 | Lisa Keim | Republican | Dixfield | Oxford | |
| 19 | James Hamper | Republican | Oxford | Oxford | |
| 20 | Ned Claxton | Democratic | Auburn | Androscoggin | |
| 21 | Nate Libby | Democratic | Lewiston | Androscoggin | |
| 22 | Jeffrey Timberlake | Republican | Turner | Androscoggin | |
| 23 | Eloise Vitelli | Democratic | Topsham | Sagadahoc | |
| 24 | Brownie Carson | Democratic | Brunswick | Cumberland | |
| 25 | Cathy Breen | Democratic | Falmouth | Cumberland | |
| 26 | G. William Diamond | Democratic | Windham | Cumberland | |
| 27 | Ben Chipman | Democratic | Portland | Cumberland | |
| 28 | Heather Sanborn | Democratic | Portland | Cumberland | |
| 29 | Rebecca Millett | Democratic | Cape Elizbath | Cumberland | |
| 30 | Linda Sanborn | Democratic | Gorham | Cumberland | |
| 31 | Justin Chenette | Democratic | Saco | York | |
| 32 | Susan Deschambault | Democratic | Biddeford | York | |
| 33 | David Woodsome | Republican | Waterboro | York | |
| 34 | Robert A. Foley | Republican | Wells | York | |
| 35 | Mark Lawrence | Democratic | South Berwick | York |