Dotted across America, these sprawling mega-mansions have it all, from breathtaking infinity pools to state-of-the-art entertainment complexes and even secret underground tunnels – and the only thing bigger than their square footage is their price tags. But when you're a billionaire, nine-figure homes are a mere drop in the ocean. Let's take a look around the most opulent homes on the market, just waiting to be snapped up by America's wealthiest buyers...

This elegant equestrian property, on the market for $100 million (£80m), is set amongst the rolling hills of the Westchester countryside, just an hour outside of New York City. Perfect for a deep-pocketed nature lover who likes to be in easy reach of the city, it's situated on 740 acres of land, making it the largest privately-owned property in Westchester County. 

In the heart of the grounds perched at the top of a hill sits the main manor house. Accessed by a long winding driveway, the four-storey residence has an opulent interior that's sure to entice any billionaire. Encompassing an enormous 24,000 square feet of space, the grand hallway leads through to the formal living room and dining area, which connects to the vast kitchen with a butler's pantry.

There are eight spacious bedrooms and eight bathrooms, but the pièce de résistance is the master suite. Situated on the third floor, it's the ideal plush private sanctuary, featuring a Japanese-inspired secret indoor garden and a luxurious limestone bathroom.

In the formal grounds, a pergola walkway leads to the impressive pool pavilion. At 4,000 square feet, it houses a 60-foot long swimming pool and spa, flanked by rows of French doors that open out onto the idyllic gardens and paddocks. In addition to the gym, sauna and changing rooms, the poolhouse also includes an inviting lounge complete with a stone fireplace, as well as a kitchen.

The perfectly maintained grounds are home to world-class equestrian facilities, which include a turf racetrack, riding trails, a 40-stall barn, pastures, pens and four paddocks. There's also a working cattle farm, ponds, orchards, a caretaker's residence and eight staff quarters, so this magnificent estate will run seamlessly without its new owner having to lift a finger.

Located on just over two-and-a-half acres of oceanside land, Mar de Amour is a dream home only billionaires can afford. Listed at $115 million (£92m), it boasts an impressive gated entryway and a long driveway that leads to an imposing courtyard, overlooked by the spectacular glass house. 

The two-storey entrance is a spectacular sight to behold. A dramatic 18-foot-long floor-to-ceiling crystal chandelier hangs at the heart of a sweeping spiral staircase, alongside engraved glass balustrades and white marble floors. How's that for a first impression?

With two separate wings connected by a central hallway, the home has an impressive 12 bedrooms and 14 bathrooms. The master suite offers a private slice of luxury, featuring a large balcony for soaking up the mesmerising ocean views.

Money was clearly no object when it came to designing this property, as it's jam-packed with world-class amenities. The state-of-the-art kitchen comes with its own private lift, while elsewhere in the mega-mansion there's a Hollywood-style 20-seater movie theatre complete with Dolby surround-sound.

If the 10,600 square feet of interior space wasn't enough, the grounds are just as spectacular. Perched on the edge of the hillside, the infinity pool is the perfect place to while away a sunny afternoon, offering spectacular vistas of the beach and ocean, a mere stone's throw away. What's more, the home also has an unbelievable underground surprise in the form of an eight-car subterranean garage.

The ultimate dream oceanfront property, this sprawling home sits on nearly three acres of land with just over 250 feet of picturesque beach frontage. Currently on the market for $125 million (£100m), it's the ideal spot to relax in privacy, with a gated entrance and guardhouse ensuring the highest levels of security.

Inside, the 3,800-square-foot main house is just as spectacular as its surroundings. With vaulted ceilings and herringbone hardwood floors, the lower level is brimming with amenities, from a spacious office, entertainment room and recording studio to a wine room and a gourmet kitchen with a butler's pantry.

Upstairs, there are three opulent ensuite bedrooms plus the master suite, which comes complete with dual baths, a walk-in wardrobe and an outdoor shower. Enjoying stunning views out across the azure waters below, the secluded pad would be suited to a wealthy buyer looking for a plush retreat to kick back and relax in.

The estate also has a luxurious three-storey guest house featuring three bedrooms, a large living room, kitchen, bathroom and even an amazing aquarium wall for marine-loving billionaires. Not a bad place to put up visitors!

Also within the grounds are a swimming pool and spa, sumptuous lawns and a basketball court, however, the mansion's most desirable feature lies below. Stairs lead down to a cabana and your own private stretch of beach with a beautiful wooden deck that sits steps away from the shoreline.

A rare, 15-acre estate that's flanked by Lake Worth and the Atlantic Ocean, Gemini is a stand-out property perched atop a dune, offering unrivaled 360-degree waterfront views. On the market for $138 million (£110m), the estate is split into two halves by a main road, however, a series of secret underground tunnels allow residents to move freely across the property – one tunnel even includes a fully-furnished gallery. 

The sprawling main house covers 62,200 square feet and boasts a number of impeccably designed living rooms. This regal space features a wow-factor wooden coffered ceiling, marble walls and back-lit shelving for the ultimate spot to grab a moment's peace.

As well as stunning reception rooms, there's plenty of luxury amenities to keep residents entertained. Numerous terraces sit alongside a state-of-the-art media room, library, office and an expansive wine cellar for those partial to a tipple. As well as all this, there are two lifts for easy access to the whole house – a necessity when your home's this big!

In addition to the 12-bedroom main residence, the estate offers two four-bedroom beachside cottages and a seven-bedroom house, as well as a guest house that's made up of four studios and apartments. In total there are more than 30 plush bedrooms, so you'll never be short of space to host guests again.

Gemini's grounds are a billionaire's playground, with everything from a swimming pool, fitness centre and a spa to a PGA-standard golf area, tennis court and basketball court. Winding pathways lead down to the beach on one side and the lake's dock and pier on the other, making it the perfect pad for boating and water sports enthusiasts too.

Its prime location is the real draw of this 42-acre estate in the sought-after New York region of The Hamptons. Jule Pond stretches along the oceanfront for a quarter of a mile, granting residents enviable sea views. The extensive $145 million (£116m) property, which includes 12 bedrooms and 12 lavish bathrooms, also overlooks three large ponds and the sapphire waters of Mecox Bay.

Originally commissioned by the Ford family (of the automobile fame), the house is all white brick and grand columns from the outside. Inside, the 20,000-square-foot interior is impeccably decorated and laid out across three wings. Particularly striking is the 48-foot-long living room with its parquet flooring, intricately carved fireplace and plush soft furnishings.

The chef's kitchen is a dream for keen cooks, featuring modern marble worktops, a generous pantry and a breakfast island. In addition to the numerous reception rooms and living areas, the property includes two sumptuous master suites, a TV room, library, gym and sauna, along with a private bar. The new owners of this luxurious estate will hardly need to leave the house... 

One of America's most amazing estates, the full scale of the property can only really be appreciated from above. In addition to the principal home, there's an additional carriage house with a further three bedrooms. The grounds also contain a detached garage with room for six cars, plus a tennis and basketball court, not to mention your own stretch of private beach.

One of our favourite features in the estate is the heated, gunite swimming pool, framed by hedges for extra privacy. Throw in a separate spa, alfresco dining areas and those waterfront views and you've got the makings of a perfect pool day.

Spread over nearly 10 acres, this Italian-style estate is on the market for $165 million (£132m). Accessed by its very own street, expansive gates open onto a jaw-dropping 30-car courtyard, making this guarded getaway the perfect private billionaire bolthole. 

Inside, the sprawling mansion has around 20,000 square feet of space featuring high ceilings and opulent finishes throughout. The grand hallway is framed by beautiful archways and grand chandeliers, with a maze of corridors leading off to the formal living rooms as well as smaller, more intimate spaces.

The 20-bedroom, 23-bathroom home isn't short of stately features – this grand living space dazzles with an ornate floor-to-ceiling fireplace, a coffered ceiling and intricate plasterwork. We can think of worse places to host a drinks party...

A sprawling four-acre garden is home to a luxury swimming pool complete with a poolhouse, a two-storey guest house and a tennis court. Surrounded by tropical palm trees and dense foliage, the outdoor space feels like a world of its own – surely one of the most incredible billionaire backyards we've seen. 

Crisscrossed by walking and jogging trails, the property also comes with a separate lot that has plenty of development potential if you fancy making the estate even grander than it currently is. Perfect for a deep-pocketed buyer in search of a private oasis in one of the most sought-after locations in the world, this Beverly Hills home is nothing short of spectacular.

Located in the city of Pampa in Texas, Mesta Vista Ranch sits within 644,000 acres of land. Once owned by T Boone Pickens, a famous oil prospector who passed away in 2019, the estate has been languishing on the market since 2017 and is now listed for a staggering $220 million (£176m). 

The owner's old residence, the 11,500-square-foot Lake House, features no end of luxury finishes, from oak vaulted ceilings and travertine flooring to a spiral staircase imported from France and even a stained-glass front door that once belonged to Bing Crosby's home. 

Elsewhere on the lot, The Lodge compound is the single largest residence amongst the numerous properties. Its 25,000-square-foot interior encompasses a 30-seater home theatre, a wine cellar, conference room and professional kitchen, opening up no end of commercial possibilities for the lavish house.

Outside, there's an additional 10,000 square feet of patios complete with bronze railings and balconies overlooking the pool and landscaped grounds. If all this wasn't enough, the ranch also has its own FAA-approved airport, which has a hangar that includes a two-bedroom, two-bathroom apartment for visiting pilots.

12 miles of idyllic waterfalls, creeks and lakes pepper the expansive lot, along with a chapel, a number of extra guest houses, a pub and even kennels. Included in the asking price are all the interior furnishings, farming equipment and several pick-up trucks, so the new owner will be ready to run this stunning ranch for sale from the get-go.

The most expensive property for sale in America at the moment, Casa Encantada is listed for a whopping $225 million (£180m). On the open market for the first time in 20 years, the home once welcomed presidents and Hollywood royalty and was previously owned by famed hotelier Conrad Hilton. The 40,000-square-foot mansion sits on eight acres of land in Bel Air and features all the billionaire trappings a super-rich buyer could wish for.

Designed by famed architect James E Dolena, the main home has an impressive 60 rooms, with each carefully designed to enjoy views of the city, ocean or gardens. Restored to its original glory, which has taken some two-and-a-half years, the interior features a dramatic entrance with 18-foot ceilings – talk about a regal welcome!

With the lower level designed for entertaining, the second storey features more comfortable family living quarters, as well as opulent home-working spaces. This grand office has a stunning marble fireplace, built-in bookshelves and floor-to-ceiling windows with French doors leading out to a private patio.

Outside, the poolhouse is home to a professional screening room, a formal bar and far-reaching views over the rose gardens and beyond. Who wouldn't want to spend their days lounging by the pool, with every amenity you could dream of at your fingertips?

Elsewhere in the grounds, there's an illuminated tennis court and a state-of-the-art basketball court that are sure to be a hit with fitness fans. A guest house sits alongside the manager's quarters, while ponds and beautiful landscaping create the ultimate natural oasis. What more could you want?