Place eggs in a saucepan and cover with cold water. Bring to a boil over high heat. Once boiling, cover the pan, remove from heat, and let sit for 9 minutes.
Transfer eggs to a bowl of ice water and let cool completely, about 5 minutes.
While eggs cool, combine diced cucumber, celery, red onion, and dill in a large bowl.
In a small bowl, whisk together lemon juice, olive oil, Dijon mustard, salt, and pepper.
Peel the cooled eggs and chop into bite-sized pieces. Add to the bowl with vegetables.
Pour the dressing over the salad and toss gently to combine. Taste and adjust seasoning if needed.
Serve immediately, or refrigerate for 30 minutes to allow flavors to meld.
