Cyber Monday Firm King Size Mattresses Sale

Shop our Cyber Monday firm king size mattress collection to compare available king mattresses with a firm feel across a range of materials, features and price points. Explore options to find the right balance of support and comfort for your sleep preferences.

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Beautyrest PressureSmart 2.0 Firm 11" Mattress

Starting at

$1099⁷⁷

$2199⁹⁹

$1100 OFF

Firm Comfort, best for

Back, Stomach Sleepers
Temperature
Bed Partner
Pain
Toss and Turn

FREE ADJUSTABLE BASE ³ with code ELEVATE

Sleepy's Basic Memory Foam Firm Mattress

3264

Starting at

$299⁷⁷

$999⁹⁹

$700 OFF

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Bed Partner
Temperature
Toss and Turn
Support

Sleepy's Basic Innerspring Firm Mattress

8709

Starting at

$249⁹⁹

Firm Comfort, best for

Back, Stomach Sleepers
Temperature
Pain
Bed Partner
Allergies
Toss and Turn

Sleepy's Basic Foam Mattress

1419

Starting at

$649⁹⁹

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Temperature
Bed Partner
Toss and Turn

FREE ADJUSTABLE BASE ³ with code ELEVATE

Beautyrest BR800 11.25" Firm Mattress

2248

Starting at

$1299⁹⁹

Firm Comfort, best for

Back, Stomach Sleepers
Toss and Turn
Pain
Bed Partner
Temperature

FREE ADJUSTABLE BASE ³ with code ELEVATE

Stearns & Foster Estate 14.5" Firm Mattress

1837

Starting at

$3099⁰⁰

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Bed Partner
Temperature
Allergies
Toss and Turn

Receive $300 Instant Gift⁴ with purchase.

Sealy Essentials Sudley 8.5" Firm Mattress

989

Starting at

$499⁷⁷

$999⁹⁹

$500 OFF

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Temperature
Bed Partner
Toss and Turn

Serta Perfect Sleeper Nurture Night 12" Firm Mattress

1200

Starting at

$999⁰⁰

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Bed Partner
Temperature
Toss and Turn

FREE ADJUSTABLE BASE ³ with code ELEVATE

Tulo Bamboo 6" Firm Green Tea Memory Foam Mattress

5578

Starting at

$259⁹⁹

$729⁹⁹

$470 OFF

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Bed Partner
Temperature
Toss and Turn

Nectar Classic 12" Firm Memory Foam Mattress

234

Starting at

$899⁰⁰

$1399⁰⁰

$500 OFF

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Bed Partner
Temperature
Toss and Turn

Sealy Essentials Spruce 5.5" Firm Mattress

1372

Starting at

$949⁹⁹

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Temperature
Bed Partner
Toss and Turn

Tempur-Pedic TEMPUR-ProAdapt 2.0 12" Firm Mattress

5077

Starting at

$4199⁰⁰

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Allergies
Bed Partner
Toss and Turn
Temperature

Receive $300 Instant Gift⁴ with purchase + Calm app 3-month free trial

Serta Perfect Sleeper Oasis Sleep 14.5" Firm Pillow Top Mattress

1195

Starting at

$1399⁰⁰

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Bed Partner
Temperature
Toss and Turn

FREE ADJUSTABLE BASE ³ with code ELEVATE

Tempur-Pedic TEMPUR-ProAdapt 12" Firm Previous Generation Mattress

6743

Starting at

$2869⁷⁷

$4099⁰⁰

$1229 OFF

Firm Comfort, best for

Back, Stomach Sleepers
Bed Partner
Pain
Temperature
Toss and Turn
Allergies

Stearns & Foster Estate 15" Firm Euro Pillow Top Mattress

2790

Starting at

$3299⁰⁰

Firm Comfort, best for

Back, Stomach Sleepers
Pain
Bed Partner
Temperature
Allergies
Toss and Turn

Receive $300 Instant Gift⁴ with purchase.

Tempur-Pedic TEMPUR-LuxeAdapt 13" Firm Previous Generation Mattress

1878

Starting at

$3429⁷⁷

$4899⁰⁰

$1469 OFF

Firm Comfort, best for

Back, Stomach Sleepers
Bed Partner
Pain
Temperature
Toss and Turn

A Cyber Monday firm king size mattress event is a smart opportunity to upgrade to spacious, supportive sleep at a seasonal value. Firm king mattresses offer a stable sleep surface with plenty of room for couples, making them a popular choice for people who prefer a more supportive feel or want to minimize motion across the bed. At Mattress Firm, shoppers can explore firm king size mattresses from trusted brands, including options with cooling materials, pressure-relieving comfort layers, responsive springs and reinforced edges. Comparing mattress construction, comfort preferences and sleep needs can help you find a king mattress that feels supportive without sacrificing comfort. Shopping during a Cyber Monday mattress event can also make it easier to save on a complete sleep setup. Along with a firm king size mattress, consider a king bed frame, adjustable base, mattress protector, pillows and sheets designed for a king bed. Review available promotions, delivery options, trial periods and warranty details before making your purchase, since event terms and product availability may vary. With a wide selection of king size mattresses and expert guidance, Mattress Firm helps make it easier to find the right firm mattress for restful nights and better days.

What is a firm mattress? + -

A firm mattress has a more solid, supportive feel with less sink than a medium or plush mattress. Its comfort comes from the combination of the comfort layers, support core and upholstery materials.

What materials are commonly used in firm mattresses? + -

Firm mattresses may include innerspring coils, memory foam, latex or hybrid layers. Each material contributes a different feel, including responsive support, pressure-relieving cushioning or enhanced airflow.

How do firm hybrid mattresses differ from firm foam mattresses? + -

Firm hybrid mattresses combine coils with foam or other comfort materials, while firm foam mattresses use layered foam throughout. Hybrids often feel more responsive, while foam models offer a more uniform surface feel.

What type of bed foundation works with a firm mattress? + -

A firm mattress typically works with a compatible platform bed, adjustable base or foundation. Check the mattress and foundation specifications to confirm compatibility before pairing them.

What bedding complements a firm mattress? + -

Breathable sheets, a comforter suited to the season and a pillow with the right loft can complement a firm mattress. Choose bedding based on your preferred warmth, texture and overall comfort.