O.N. Athletics
24/7 GYM • STRENGTH TRAINING • CROSSFIT
A 24/7 Gym in Groton & Mystic, CT
Home of CrossFit DYR
O.N. Athletics is a 7,200+ sq. ft. 24/7 gym in Groton, CT, located on the Groton side of Mystic and serving Groton, Mystic, Ledyard, Gales Ferry and surrounding communities. Train independently with 24/7 open gym access, build strength with our extensive commercial equipment, join coach-led CrossFit DYR classes, or work one-on-one with a personal trainer.
5.0 from 205 Google reviews
Open 24/7
7,200 sq. ft.
Locally owned
Serving Groton & Mystic
Four Ways In
Choose How You Train
24/7 Open Gym
Train independently whenever your schedule allows with 24/7 access to our full facility.
Strength Training
Train with extensive commercial strength equipment, free weights, barbells, machines, cables and more.
CrossFit
CrossFit DYR
Coach-led CrossFit classes for beginners through experienced athletes.
Personal Training
One-on-one coaching built around individual goals, with 24/7 gym access included with personal training memberships.
Also Available
Youth Athletics
Speed, strength, and movement training for young athletes, with safe progressions that build confidence.
Recovery & Sauna
On-site sauna and recovery tools that keep you training consistently between sessions.
Nutrition Coaching
A practical nutrition plan with ongoing accountability so what you eat supports the work you put in.

The Facility
7,200 Square Feet, Open Around The Clock
- 7,200+ sq. ft.
- Open training floor with room to move
- Racks & platforms
- Squat racks, lifting platforms, and bumper plates
- Free weights
- Full dumbbell and barbell ranges with benches
- Machines
- Plate-loaded, selectorized, and cable machines
- Cardio
- Rowers, bikes, treadmills, and conditioning machines
- Open training area
- Sled pushes, carries, and sprint work
- Sauna
- On-site recovery after your session
- Free parking
- On-site lot, no meters, no garages
- Member app entry
- Secure member access any hour of the day
See what open gym includes on the 24/7 gym in Groton page, or read about the strength floor.
Don't Just Take Our Word For It
What Our Members Say
Real reviews from real members in Groton and Mystic
Rojuan Henry
a week ago
It’s an amazing environment for your work out session
Luis Bonet
a week ago
I’ve been to 5 different gyms and by far this gym is the best gym I’ve been to.
Emerson Adams
a week ago
Very clean gym, great new equipment, private/exclusive location. Best gym around the area! Great owners.
⭐ 5.0 from 205 reviews on Google
Take The First Step
Start Your Journey Today
Fill out the form below and schedule your FREE intro session. A coach will reach out to get you started at Groton's premier 24/7 gym.
Getting Started Is Easy
Are You Ready To Level Up?
Step 1
Book Your Free Intro
Fill out the form and schedule a time to come in. We'll show you around the facility, learn about your goals, and answer every question you have.
Step 2
Find Your Fit
Open gym, strength training, personal training, or CrossFit Dýr classes, on their own or combined. We'll match you with the program and membership that fits your goals and your schedule.
Step 3
Start Training
Pick your class times or activate 24/7 access in our member app and get to work. From day one you'll have coaching, community, and a facility built to help you succeed.
Find Us
Come Visit Us
Address
800 Flanders Road, Building 9 Unit 5
Mystic, CT 06355
Serving Groton, Mystic, Noank, Stonington, New London, Ledyard, Gales Ferry & Southeastern Connecticut
Directions & Parking
Off Flanders Road, connecting to Routes 184 and 1, minutes from downtown Mystic and a short run from I-95, Noank, Stonington, New London, and Naval Submarine Base New London. Free on-site parking directly outside the door.
Get driving directionsCall or Text
(860) 415-4909Hours
Open 24 Hours7 Days a Week
24/7 member access through our member app
Driving in from the coast? Read our Gym In Mystic page, grab a $15 day pass, or call or text (860) 415-4909.
Common Questions
Frequently Asked Questions
No. Members here range from people walking into a gym for the first time to lifelong athletes. Your free intro starts with a conversation about where you are today, and we build from there.
Yes. Members get 24/7 member app access to the full 7,200+ sq. ft. floor 24 hours a day, seven days a week, so you can train at 4 AM before a shift or at 10 PM after the kids are down.
Squat racks, lifting platforms, bumper plates, a full dumbbell and barbell range, benches, plate-loaded, selectorized and cable machines, rowers, bikes, treadmills, open training area, and an on-site sauna.
No. Most members train on their own or with a personal trainer. CrossFit DYR classes are here whenever you want coached group training, and you can add them later or never at all.
We deliberately cap membership to help reduce overcrowding and maintain a comfortable training environment with better access to equipment and training space. Member schedules also spread across the whole clock, from pre-dawn lifters to overnight shift workers. Early evening is honestly our busiest window, and the quietest hours are late night and early morning.
Yes. We deliberately cap membership to help reduce overcrowding and maintain a comfortable training environment with better access to equipment and training space.
Yes, two ways. Your first intro session is free and includes a tour and a conversation with a coach, or you can buy a $15 open gym day pass and train on your own for a visit. Details are on the drop-in page.
Our CrossFit DYR coaches and personal trainers all coach here full time and carry current certifications. Ask at your free intro and we will match you with the coach whose background fits your goals.
Book a free intro, come in for a tour and a conversation about your goals, then pick the membership that matches how you want to train. You can start the same day.
Open gym starts at $45/month, CrossFit DYR classes start at $150/month, and personal training starts at $70/session. Military, first responder, family, and student rates are available, ask at your free intro.
Yes. Building muscle raises the amount of energy your body uses at rest, and strength work paired with conditioning and sensible nutrition is one of the most reliable ways to change body composition and keep it there.
We are at 800 Flanders Road, Building 9 Unit 5, Mystic, CT 06355. Flanders Road runs parallel to Route 117 and connects to Routes 184 and 1, so we are minutes from downtown Mystic. Parking is free and on-site, right outside the door.
Still Not Convinced?
We'll make it easy






