Pequot Runners Thanksgiving Day Road Race in Southport (Fairfield County)
5-mile run and 2.6-mile walk 
This scenic fast, course goes through the Gold Coast and has some of the state's loveliest views, including Southport Harbor. The Pequot Running Club was founded in 1978, and welcomes all ages and abilities. Due to security concerns, the organizers ask that both participants and spectators bring transparent bags to avoid delays. The field will be limited to 7,000 runners. 
385 Center Street, Southport. 8:15am start. 

Goshen Turkey Trot (Litchfield County) 10K run 
This 6.2-mile run this has turned into one of Litchfield County's best traditions for over three decades at the Goshen Fairgrounds. The course is difficult, but promises to be rewarding! You'll enjoy picturesque scenery going through farms, woods and hilly countryside. An enthusiastic crowd will cheer you on, and after enjoy the bonfire, cider and donuts. 
116 Old Middle Street, Goshen. 9am start. 

Madison Turkey Trot (New Haven County)
5-mile run and 2-mile family fitness walk 
If you are looking to set a PR (personal record) this race might be for you! It is a very flat course that starts at the West Beach area of beautiful Hammonasset State Park. They have an efficient plan in place, having the 2-mile walk start after the run, and on a different course. I hear the post-race food is the best around! The park will close to cars at 930am so like the other events, don't get stuck in traffic and miss the race!
1288 Boston Post Road, Madison. Run starts at 10am; walk at 10:05am. 

Manchester Road Race (Hartford County) 4.7-mile run/walk
This is the mother of all Thanksgiving day races, a Connecticut tradition for 77 years. You and your closest 14,999 friends will crowd in and run or walk 4.7 miles. Many people dress in costume and even swig beers along the route. Seasoned runners participate, but it also brings out the amateurs in search of a party. It is a festive atmosphere, with fans cheering and bands playing along the way. Unless you have qualified for an elite starting time, it is very crowded and can be frustrating. In the starting gate, I heard the woman next to me say "I can't remember the last time I ran five miles." I thought she was kidding. She was not. It can be a wonderful experience and a bucket list item (especially after you climb the big hill) but beware of dealing with the masses. 
Main Street, Manchester. 10am start. 

Run Turkey Run! in Hamden (New Haven County) 10K/5K
7:30am comes early for this race, so be sure to set multiple alarms. You don't want to pull a Jean-Paul from Seinfeld. You'll race on the paved Farmington Canal Trail. The courses are mostly flat, with a few rolling hills. You'll get your blood flowing and be done in time to get the turkey in the oven or hit a high school football game. 
Behind Multisports Academy, 109 Sanford Street, Hamden. 730am start. 

Mystic Turkey Trot and Dip (New London County)  3-mile and 1-mile walk/run
Sponsored by the Mystic Branch of the Ocean Community YMCA, this is one of the more reasonably-priced Thanksgiving Day races. Early registration is only $15; with $20 on race day.Now a 21-year tradition, you have the option of ending your day with a dip. Not the onion or spinach variety, but a plunge in the Mystic River. Why not? It is just like the Pilgrims used to do. Ok maybe not, but the brisk water will feel good after you work up a sweat. If nothing else, you'll get to start Thanksgiving off in one of New England's most scenic and beloved towns. 
One Harry Austin Drive, Mystic. 830am start.