Eight members of the cast were honored by the mayor of A.C., Marty Small, outside the Hard Rock Hotel & Casino ... where he legitimized "Jersey Shore" Day, a.k.a "Jerzday."

The ceremony drew a crowd of pumped-up fans ... waving Italian flags and hoisting posters of 'JS' favorites like Snooki, Vinny and JWoww, who were in attendance.

In fact, all 8 cast members from the current "Jersey Shore: Family Vacation" were in attendance, including Mike "The Situation" Sorrentino, Pauly D, Angelina Pivarnick, Deena Cortese and Sammi "Sweetheart" Giancola.

Mayor Small explained why the cast deserves such an honor ... "Because in the last 15 years, this group has made New Jersey proud with strength, perseverance, family values, gym, tan, laundry."

Clearly, the Mayor appreciates the amount of attention the show has drawn to the city over the years. In fact, the reality show's spin-off, "Family Vacation," recently filmed in A.C.