Which ship should you actually book?
All four ships share the core Millennium Class structure. The real decision, as I see it, comes down to data quality, refit recency, and whether a dedicated Retreat Sundeck matters to you.
Want the class original, and don’t mind less-reliable published cabin data?
I’d point you to Celebrity Millennium — the class namesake, though this ship’s own cabin-count data is the least internally consistent of the four.
Want a Sunset Suite specifically?
Celebrity Infinity or Celebrity Constellation both have one — Celebrity’s own site disputes which ship (if either) it’s truly exclusive to, and neither ship has a dedicated Retreat Sundeck.
Want the ship with a dedicated Retreat Sun Deck since 2019?
Celebrity Summit is my pick — though even this ship’s stateroom total is pre- vs. post-refit (1,079 vs. 1,109), a nuance a follow-up audit found I’d originally missed.
Want the newest ship in the class and the most recent refit?
Celebrity Constellation — refreshed April 2024, though it also lacks a dedicated Retreat Sundeck.
Four questions, then a starting point
Four ships, one shared skeleton, and genuinely different refit histories. Answer these and I’ll tell you which one I’d start pricing first.
Which Millennium Class ship fits you?
Four questions about what actually matters to you on this class, then a specific ship — not a shrug.
The most uneven Retreat rollout of any Celebrity class
Millennium Class ships are structurally similar, but each has a distinct refit history and, in my assessment, a genuinely different Retreat Sundeck status.
| Ship | In service | Staterooms | Retreat Sundeck status |
|---|---|---|---|
| Celebrity Millennium | 2000 | ~1,079 (the least reliable data in the class — one source is internally inconsistent) | Dedicated Sundeck added in the 2019 refit |
| Celebrity Infinity | 2001 | 1,085 | Confirmed absent, despite a January 2024 Retreat-focused refit — has a Sunset Suite, though Celebrity’s own site disputes its exclusivity to this ship |
| Celebrity Summit | 2001 | 1,079 pre-refit / 1,109 post-2019-refit (a newer Celebrity fact sheet, matching Wikipedia’s capacity figure) | Dedicated Sun Deck added in the 2019 refit |
| Celebrity Constellation | 2002 | ~1,065 (the best-supported of three disputed figures I found) | Confirmed absent, despite an April 2024 refit — also has a 12-cabin Sunset Suite, though exactly when/how it arrived is less clear than I first presented |
This class showed me the widest and most frequent cabin-count disagreements of any Celebrity class in this research project — see each ship’s own page for the full breakdown and the specific figures I chose not to use.
Has a dedicated Retreat Sundeck
- Added via 2019 refits on both ships
- A dedicated outdoor deck for suite guests, beyond the Retreat Lounge and Luminae
- Summit is the better-documented of the two — Millennium’s overall stateroom data is the least reliable in the class
- Neither of these two ships has a Sunset Suite
No dedicated Retreat Sundeck
- Confirmed absent on Celebrity’s own current site for both ships, despite recent Retreat-focused refits (January 2024 for Infinity, April 2024 for Constellation)
- Both ships instead carry a 12-cabin Sunset Suite — a category Celebrity’s own site can’t consistently confirm as exclusive to either one
- The refits improved the Retreat Lounge and dining side of the program, not the outdoor deck
Interior through the Retreat suite tiers
Every Millennium Class ship, as I understand it, runs Interior, Ocean View, Veranda (branded "Deluxe Ocean View" on some official fact sheets), Concierge Class, AquaClass, and a four-tier Retreat suite structure (Sky Suite, Celebrity Suite, Royal Suite, Penthouse Suite) — plus a Sunset Suite on both Infinity and Constellation, a category Celebrity’s own dedicated marketing page reads as Infinity-exclusive even though Constellation’s own Retreat page lists one too (as does Celebrity Silhouette, a different, Solstice Class ship).
Unlike the newer Solstice and Edge classes, where these categories were part of the original design, every Millennium Class ship added AquaClass via a later refit (typically converting existing balcony cabins) — most commonly during the class-wide "Solsticizing" program in the early-to-mid 2010s.
Two ships have a dedicated Sundeck, two confirmed do not
Luminae (the Retreat’s suite-exclusive restaurant) and a Retreat Lounge exist on all four ships, but a dedicated suite-guest Retreat Sundeck does not. Millennium and Summit both received one via their respective 2019 refits. Infinity and Constellation both had substantial, more recent Retreat-focused refits (January 2024 and April 2024 respectively) — but neither added a dedicated Sundeck, which I’ve confirmed directly on Celebrity’s own current site for both ships.
Ships with a dedicated Retreat Sundeck
Millennium (since 2019) and Summit (since 2019).
Ships confirmed WITHOUT a dedicated Retreat Sundeck
Infinity and Constellation — both had recent Retreat-focused refits that improved the lounge and dining experience without adding a suite-exclusive outdoor deck.
Consistently 26 per ship
Every ship in this class reports 26 wheelchair-accessible staterooms — one of the most consistent figures I found across any Celebrity class, corroborated by at least two independent sources on every ship.
I’d confirm the exact accessible cabin number, category and door width directly with Celebrity or a travel advisor well ahead of your sailing.
No confirmed ship-exclusive venue on any of the four ships
Blu (AquaClass-exclusive), Luminae (Retreat-exclusive), Tuscan Grille, Qsine (with Le Petit Chef), Sushi on Five, Café al Bacio, Mast Grill and Spa Café are shared across all four ships, per a cross-ship dining guide that explicitly confirms these venues are common fleet-wide within this class. Each ship’s main dining room carries a distinct name (Metropolitan on Millennium, Trellis on Infinity, San Marco on Constellation), and my research found no dining venue genuinely exclusive to any single ship in the class.
Start with Summit
It’s the most consistently well-documented ship in the class — pick a priority above and I’ll narrow it down further.
What does the next dollar actually buy?
A window with no balcony — every ship in this class. Simple as that.
Private outdoor space — the standard upgrade class-wide, and the one I’d default to if a balcony matters to you at all.
Priority perks or wellness extras plus Blu access — both retrofitted categories on every ship in this class, so I wouldn’t expect either to feel "built-in."
Full Retreat restaurant and lounge access on every ship — but I’d remind you a dedicated Sundeck only exists on Millennium and Summit.
The top of the ladder class-wide.
Make the upgrade prove itself
Use the Celebrity Add-On Value Evaluator alongside this guide — the cabin library above gives you the facts, and the evaluator tells you whether the price gap between two categories is actually worth paying.
Celebrity Add-On Value Evaluator
Open the Celebrity value tool and apply it to the cabin premium you are actually deciding on.
Pick your ship for the full breakdown
Celebrity Millennium
The class original, since 2000 — genuinely inconsistent published cabin data.
Celebrity Infinity
Has a Sunset Suite (disputed exclusivity) — but no dedicated Retreat Sundeck.
Celebrity Summit
The best-documented ship in the class, with a dedicated Retreat Sun Deck.
Celebrity Constellation
The newest ship — refreshed April 2024, also has a 12-cabin Sunset Suite and also lacks a dedicated Sundeck.
Millennium Class cabin questions
What is the difference between Millennium Class ships?
All four share the same core cabin structure, but each has a distinct refit history — most notably, only Millennium and Summit have a dedicated Retreat Sundeck, while Infinity and Constellation confirmed do not, despite both having had recent Retreat-focused refits.
Which Millennium Class ships have a dedicated Retreat Sundeck?
Only Celebrity Millennium and Celebrity Summit, both added in 2019 refits. Celebrity Infinity and Celebrity Constellation are both confirmed to lack this feature, directly per Celebrity’s own current site.
What is the Sunset Suite, and is it really Infinity-exclusive?
A Retreat-tier suite found on Celebrity Infinity (12 cabins, elevated to full Retreat status in a January 2024 refit) and Celebrity Constellation (also 12 cabins, though exactly when it arrived is less clear than I first presented) — and on Celebrity Silhouette, a different, Solstice Class ship. Celebrity’s own dedicated Sunset Suite marketing page reads as exclusive to Infinity, but the other ships’ own current Retreat pages directly contradict that — a self-contradiction on Celebrity’s own site I’m not resolving for you.
Do Millennium Class ships have AquaClass?
Yes, on all four ships — but as a retrofit, not part of the original design. Every ship in this class added AquaClass via a later refit, typically converting existing balcony cabins.
How reliable is the published cabin-count data for this class?
Less reliable than for Celebrity’s newer classes, in my experience — this class showed the widest and most frequent cross-source disagreements in this entire research project, particularly on Celebrity Millennium, where one major tracker is internally inconsistent on its own page.
My own research — verify specifics before booking
This page is my own research into Celebrity’s published stateroom data across all four Millennium Class ships, cross-checked against third-party cruise sources current as of August 2026 — I’m not presenting it as a locked or pre-audited document.
Every ship in this class shows real, unresolved stateroom-count disagreement between third-party trackers — Celebrity Millennium’s is the worst, with one source internally inconsistent on its own page.
The Retreat Sundeck’s presence or absence is genuinely uneven across this class and easy to get wrong if you only check one source — I cross-checked each ship’s status against Celebrity’s own current site directly.
CruiseMapper contains at least one templated-looking claim (a "2020 Celebrity Revolution overhaul" on Constellation) contradicted by more specific sources — I flagged it on that ship’s own page rather than using it here.
Celebrity Summit’s stateroom total is genuinely pre- vs. post-2019-refit (1,079 vs. 1,109) — a nuance an earlier version of this page missed by presenting 1,079 as simply "the cleanest figure in the class."
Celebrity Constellation’s Sunset Suite is confirmed present (12 cabins), but exactly when and how it arrived is less clear than an earlier version of this page presented — see Constellation’s own page.
The Retreat Sundeck’s presence on Millennium/Summit but absence on Infinity/Constellation is confirmed on Celebrity’s own current site. The Sunset Suite’s exclusivity to Infinity is NOT reliably confirmed — Celebrity’s own dedicated marketing page reads that way, but Constellation’s and Silhouette’s own Retreat pages both directly contradict it.
The 26-accessible-cabin figure and the core AquaClass/Concierge Class category structure are consistent across every ship in this class, as far as I could verify.
Why this class’s cabin-count data deserves more scrutiny than Celebrity’s newer classes, and which ship makes sense depending on how much the Retreat Sundeck specifically matters to you — those are my own conclusions, not numbers I found written down somewhere.