Senate Seniority List: 115th Congress
Source: http://www.senate.gov/artandhistory/history/resources/pdf/chronlist.pdf
Senate rank is first determined by the length of consecutive service in the Senate. For senators who entered the Senate on the same day, several tie-breaking procedures determine seniority. In order of precedence, these factors are: previous Senate service, service as the vice president, previous House service; service in the Cabinet, service as a state governor. If a tie still exists, senators are ranked according to the population of their state at the time of swearing in.
| Rank | All 100 Senators | Date Service Began |
| 1 | Patrick J. Leahy, D-VT | Jan. 3, 1975 |
| 2 | Orrin G. Hatch, R-UT | Jan. 3, 1977 |
| 3 | Charles E. Grassley, R-IA | Jan. 3, 1981 |
| 4 | Mitch McConnell, R-KY | Jan. 3, 1985 |
| 5 | Richard C. Shelby, R-AL | Jan. 3, 1987 |
| 6 | Dianne Feinstein, D-CA | Nov. 4, 1992 |
| 7 | Patty Murray, D-WA | Jan. 3, 1993 |
| 8 | James M. Inhofe, R-OK | Nov. 16, 1994 |
| 9 | Ron Wyden, D-OR | Feb. 6, 1996 |
| 10 | Pat Roberts, R-KS | Jan. 3, 1997 |
| 11 | Richard J. Durbin, D-IL | Jan. 3, 1997 |
| 12 | Jack Reed, D-RI | Jan. 3, 1997 |
| 13 | Susan Collins, R-ME | Jan. 3, 1997 |
| 14 | Michael B. Enzi, R-WY | Jan. 3, 1997 |
| 15 | Charles E. Schumer, D-NY | Jan. 3, 1999 |
| 16 | Michael D. Crapo, R-ID | Jan. 3, 1999 |
| 17 | Bill Nelson, D-FL | Jan. 3, 2001 |
| 18 | Thomas R. Carper, D-DE | Jan. 3, 2001 |
| 19 | Debbie Stabenow, D-MI | Jan. 3, 2001 |
| 20 | Maria Cantwell, D-WA | Jan. 3, 2001 |
| 21 | John Cornyn, R-TX | Dec. 2, 2002 |
| 22 | Lisa Murkowski, R-AK | Dec. 20, 2002 |
| 23 | Lindsey Graham, R-SC | Jan. 3, 2003 |
| 24 | Lamar Alexander, R-TN | Jan. 3, 2003 |
| 25 | Richard M. Burr, R-NC | Jan. 3, 2005 |
| 26 | John Thune, R-SD | Jan. 3, 2005 |
| 27 | Johnny Isakson, R-GA | Jan. 3, 2005 |
| 28 | Robert Menendez, D-NJ | Jan. 17, 2006 |
| 29 | Benjamin L. Cardin, D-MD | Jan. 3, 2007 |
| 30 | Bernie Sanders, I-VT | Jan. 3, 2007 |
| 31 | Sherrod Brown, D-OH | Jan. 3, 2007 |
| 32 | Bob Casey, D-PA | Jan. 3, 2007 |
| 33 | Bob Corker, R-TN | Jan. 3, 2007 |
| 34 | Claire McCaskill, D-MO | Jan. 3, 2007 |
| 35 | Amy Klobuchar, D-MN | Jan. 3, 2007 |
| 36 | Sheldon Whitehouse, D-RI | Jan. 3, 2007 |
| 37 | Jon Tester, D-MT | Jan. 3, 2007 |
| 38 | John A. Barrasso, R-WY | Jun. 22, 2007 |
| 39 | Roger Wicker, R-MS | Dec. 31, 2007 |
| 40 | Tom Udall, D-NM | Jan. 3, 2009 |
| 41 | Jeanne Shaheen, D-NH | Jan. 3, 2009 |
| 42 | Mark Warner, D-VA | Jan. 3, 2009 |
| 43 | Jim Risch, R-ID | Jan. 3, 2009 |
| 44 | Jeff Merkley, D-OR | Jan. 3, 2009 |
| 45 | Michael Bennet, D-CO | Jan. 21, 2009 |
| 46 | Kirsten Gillibrand, D-NY | Jan. 26, 2009* |
| 47 | Joe Manchin, D-WV | Nov. 15, 2010 |
| 48 | Chris Coons, D-DE | Nov. 15, 2010 |
| 49 | Roy Blunt, R-MO | Jan. 3, 2011 |
| 50 | Jerry Moran, R-KS | Jan. 3, 2011 |
| 51 | Rob Portman, R-OH | Jan. 3, 2011 |
| 52 | John Boozman, R-AR | Jan. 3, 2011 |
| 53 | Pat Toomey, R-PA | Jan. 3, 2011 |
| 54 | John Hoeven, R-ND | Jan. 3, 2011 |
| 55 | Marco Rubio, R-FL | Jan. 3, 2011 |
| 56 | Ron Johnson, R-WI | Jan. 3, 2011 |
| 57 | Rand Paul, R-KY | Jan. 3, 2011 |
| 58 | Richard Blumenthal, D-CT | Jan. 3, 2011 |
| 59 | Mike Lee, R-UT | Jan. 3, 2011 |
| 60 | Dean Heller, R-NV | May 9, 2011 |
| 61 | Brian Schatz, D-HI | Dec. 26, 2012 |
| 62 | Tim Scott, R-SC | Jan. 2, 2013** |
| 63 | Tammy Baldwin, D-WI | Jan. 3, 2013 |
| 64 | Jeff Flake, R-AZ | Jan. 3, 2013 |
| 65 | Joe Donnelly, D-IN | Jan. 3, 2013 |
| 66 | Chris Murphy, D-CT | Jan. 3, 2013 |
| 67 | Mazie Hirono, D-HI | Jan. 3, 2013 |
| 68 | Martin Heinrich, D-NM | Jan. 3, 2013 |
| 69 | Angus King, I-ME | Jan. 3, 2013 |
| 70 | Tim Kaine, D-VA | Jan. 3, 2013 |
| 71 | Ted Cruz, R-TX | Jan. 3, 2013 |
| 72 | Elizabeth Warren, D-MA | Jan. 3, 2013 |
| 73 | Deb Fischer, R-NE | Jan. 3, 2013 |
| 74 | Heidi Heitkamp, D-N.D. | Jan. 3, 2013 |
| 75 | Edward Markey, D-MA | Jul. 16, 2013 |
| 76 | Cory Booker, D-NJ | Oct. 31, 2013 |
| 77 | Shelley Moore Capito, R-WV | Jan. 3, 2015 |
| 78 | Gary Peters, D-MI | Jan. 3, 2015 |
| 79 | Bill Cassidy, R-LA | Jan. 3, 2015 |
| 80 | Cory Gardner, R-CO | Jan. 3, 2015 |
| 81 | James Lankford, R-OK | Jan. 3, 2015 |
| 82 | Tom Cotton, R-AR | Jan. 3, 2015 |
| 83 | Steve Daines, R-MT | Jan. 3, 2015 |
| 84 | Mike Rounds, R-SD | Jan. 3, 2015 |
| 85 | David Perdue, R-GA | Jan. 3, 2015 |
| 86 | Thom Tillis, R-NC | Jan. 3, 2015 |
| 87 | Joni Ernst, R-IA | Jan. 3, 2015 |
| 88 | Ben Sasse, R-NE | Jan. 3, 2015 |
| 89 | Dan Sullivan, R-AK | Jan. 3, 2015 |
| 90 | Chris Van Hollen, D-MD | Jan. 3, 2017 |
| 91 | Todd Young, R-IN | Jan. 3, 2017 |
| 92 | Tammy Duckworth, D-IL | Jan. 3, 2017 |
| 93 | Maggie Hassan, D-NH | Jan. 3, 2017 |
| 94 | Kamala Harris, D-CA | Jan. 3, 2017 |
| 95 | John Kennedy, R-LA | Jan. 3, 2017 |
| 96 | Catherine Cortez Masto, D-NV | Jan. 3, 2017 |
| 97 | Tina Smith, (D-MN) | Jan. 3, 2018 |
| 98 | Doug Jones, (D-AL) | Jan. 3, 2018 |
| 99 | Cindy Hyde-Smith, (R-MS) | Apr. 2, 2018 |
| 100 |
* Kirsten Gillibrand was appointed on January 23, 2009. She resigned her House seat on January 26, and was sworn into office on January 27, 2009.
** Tim Scott was appointed on January 2, 2013, and resigned his House seat that same day. He was sworn into office on January 3, 2013.
