SAN FRANCISCO — On a day when Apple showed off lots of new devices, the iPhone was still the star of the show.

Timothy D. Cook, Apple’s chief executive, presented the latest version of the company’s iPhone on Wednesday, along with several revamped devices in an event in the spacious Bill Graham Civic Auditorium.

Mr. Cook called the new phones, “the most advanced smartphones in the world.”

Apple executives demonstrated most of the anticipated new features of the iPhone 6S and 6S Plus, including an upgraded, 12-megapixel camera and a new capability called 3D Touch. It can sense how hard a user is pressing a button, allowing for easier access to different menus and information. It also gives users “tactile feedback” when they touch their screens. Pressure-sensitive touch screens are already available on the Apple Watch and the new MacBook.

The new iPhones will also come in a new rose gold finish, with a new glass that company describes as the strongest in the industry.

The touch ID sensor has been upgraded and the phone will feature iOS 9, the newest version of Apple’s mobile operating system.

Your Questions: Apple’s New Products

Brian X. Chen and J.D. Biersdorfer are taking questions today on Apple’s panoply of just-announced products. They will answer the questions tomorrow.

The new iPhone 6S will cost $199 and the iPhone 6S Plus will cost $299 with a phone contract. Prices for previous versions of the iPhone will drop by $100.

Apple introduced its own payment plan called Apple Care Plus. Starting at $32 a month, customers can upgrade their phones every year if they buy them through Apple. The new phones will be available in 12 countries, including the United States, on Sept. 25. They will be available for pre-order starting Sept. 12.

When Apple unveils its latest iPhones each September, investors closely watch changes to the device in the hope they will be enough to draw in new or repeat buyers. The iPhone, which was first sold in 2007, accounted for 56 percent of the company’s sales in fiscal 2014, making it far and away Apple’s most important product.

Thanks to the first iteration of the larger-screen iPhone 6 that hit shelves last year, Apple’s fourth quarter of fiscal 2014, when the company had an $18 billion profit, was the most profitable quarter ever for a publicly traded company.

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“Investors have been rewarded by assuming Apple can continually push the envelope on what a phone and the company can do,” said Michael A. Sansoterra, the chief investment officer at Silvant Capital Management, which owns Apple stock.

But meeting those expectations is becoming a bigger challenge. In its most recent quarter, Apple posted quarterly revenue of $49.6 billion and a $10.7 billion profit; iPhone revenue was up 59 percent from the previous year. But those results still fell short of Wall Street estimates, and Apple’s share price tumbled 4 percent in the following day of trading.

Mr. Cook also presented a new, beefed-up Apple TV, which represents the company’s most ambitious effort yet to become the focal point of home entertainment systems. Apple TV already streams videos and music. Now it is set to offer up video games, shopping and travel tools, and user-generated content like live streaming through an expanded array of apps.

“Our vision for TV is simple,” Mr. Cook said. “We believe the future of television is apps.

The Future of Touch Beyond Apple Watch

The new version of Apple TV also includes a remote control that could be used as a video game controller. The product now comes with a higher price tag that starts at $149, up from $69, indicating that the company is betting that consumers will think all of the new bells and whistles are worth the higher price.

Apple also introduced a new iPad Pro tablet device, which Mr. Cook called “the most capable” tablet the company has ever created. With a larger screen and optional keyboard (a feature already found in other tablet devices, like the Microsoft Surface), it becomes a device that’s more useful for the creation of content rather than simply the consumption of content.

“It makes sense for Apple to reveal a new keyboard along with new, larger-screen iPads with faster processors,” said Toni Sacconaghi, an analyst at Sanford C. Bernstein & Company. “The message being that Apple is trying to push the iPad to be more of a PC replacement, a converged device of a tablet notebook that has broader computing powers.”

Mr. Sacconaghi added that Apple had long rejected the idea that it would create such a device, but that some of the pieces were already in place. The iPad now runs Microsoft Office software and has a faster processor so it can handle more complex computing tasks.

Apple’s senior vice president of operations, Jeff Williams, also talked about improvements to the Apple Watch, including a spate of new apps including Facebook Messenger and Airstrip, a health care app that lets doctors coordinate patient care and monitor health data.

Drawing all of these devices together is Apple’s voice assistant technology, called Siri, with improved search capabilities that were prominently displayed throughout the event, especially on the new Apple TV.

Befitting the Graham auditorium’s history as a music venue, the Apple event also featured a performance from the pop band OneRepublic.