At age 11, Cyrus learned about the casting for what became Hannah Montana, a Disney Channel children's television series about a school girl with a secret double life as a teen pop star. Cyrus sent in a tape auditioning for the show's best friend role, but received a call asking her to audition for the lead, "Chloe Stewart". After sending in a new tape and flying to Hollywood for further auditions, Cyrus was told that she was too young and too small for the part. However, her persistence and ability to sing in addition to act led the show's producers to invite her back for further auditions. Cyrus eventually received the lead, renamed "Miley Stewart" after herself, at the age of twelve. Hannah Montana became an instant hit and propelled Cyrus to teen idol status, according to The Daily Telegraph. The series premiered on March 24, 2006, to the largest audience ever for a Disney Channel show and soon became one of the highest-rated series on basic cable, elevating Cyrus's wealth and fame along with it. Time magazine reports that Cyrus's "phenom[enal]" success is due partially to her talent and partially to "Disney learning to use its vast, multimedia holdings" and market Cyrus and Hannah Montana appropriately.
In 2009, Cyrus starred as Miley Stewart/Hannah Montana in Hannah Montana: The Movie. Cyrus had already begun transitioning to a more grown-up image in late 2008, when her representatives negotiated a deal for novelist Nicholas Sparks to write the screenplay and novel basis for a film that would serve as a star vehicle for Cyrus by introducing her to audiences older than the young fans she had gained through Hannah Montana. Sparks and co-writer Jeff Van Wie developed The Last Song. It was important to Cyrus that she not be type cast as a singer: "I didn't want to be a singer in another film. I don't want to do that anymore. You have no idea how many musicals show up on my door. I want to do something a little more serious." Production on The Last Song lasted from June 15, 2009, to August 18, 2009. Cyrus starred in The Last Song, which was released on March 31, 2010 and received generally poor reviews, as did Cyrus's performance. Nonetheless, the film was commercially successful, grossing more than $88 million at the worldwide box office. According to box-office analyst Exhibitor Relations, the film marked "a successful transition to adult roles for Miley Cyrus. During this time period, production on the fourth and final season of Hannah Montana began. The fourth and final season began airing on Disney Channel on July 11, 2010, and concluded on January 16, 2011.
Following the release of Can't Be Tamed, Cyrus confirmed she would be taking a break from her music career, opting rather to focus on acting. She commented, "I've not taken, like, acting lessons or anything, but it doesn't mean I don't need to because I'm sure I do [...] I'm probably going to go book an acting coach." She later confirmed she would not be going to college for the time being, stating "I'm a firm believer that you can go back at any age you want, because my Grandma went back to college at 62 [...] For right now, I really want to focus on my career. I've worked hard to get to where I am now, and I want to enjoy it while it lasts." Cyrus hosted Saturday Night Live on March 5, 2011, where she performed in several sketches. She later made an appearance on the MTV series Punk'd, appearing alongside Kelly Osbourne and Khloé Kardashian. In 2012, Cyrus appeared in the film LOL, starring alongside Demi Moore. Cyrus portrayed Lola, a teenage girl who experiments with drinking, drugs, and various sexual acts. The film received a limited release, and was critically and commercially unsuccessful. Cyrus later starred in the comedy film So Undercover, appearing as an FBI agent who is required to go undercover at a college sorority. The film was released direct-to-video in the United States on February 5, 2013. It was also reported on August 2, 2011, by Contact Music that Cyrus has signed on to star in a comedy in which she plays a woman who broke a promise to God; the film has yet to be released.
The theme song for Hannah Montana, known as "The Best of Both Worlds", was released on March 28, 2006. "The Best of Both Worlds" is credited to "Hannah Montana", the pop star Cyrus portrays on the series by the same name. As with other songs credited to Montana, Cyrus typically dressed as the character when performing the song live. The song became Cyrus' first charting song, when it debuted at number 92 on the Billboard Hot 100. The song also had success in countries such as the UK and Ireland, where it peaked at number 43 and 17, respectively. Dressed as Hannah Montana, Cyrus opened for The Cheetah Girls on twenty dates of their The Party's Just Begun Tour, beginning on September 15, 2006. On October 24 of same year, Walt Disney Records released the first Hannah Montana soundtrack. Of the nine tracks on the soundtrack performed by Cyrus, eight were credited to "Hannah Montana" and one, a duet with her father titled "I Learned from You", was credited to Cyrus as herself. Cyrus's first release under her own name had been a cover of James Baskett's "Zip-a-Dee-Doo-Dah", released on April 4, 2006, on the fourth edition of DisneyMania. The soundtrack immediately proved to be a success, debuting at number one on the U.S. Billboard 200 chart with first week sales of 281,000 copies. The album managed, to stay at the top of the chart during its second week, and went on to sell over 3.7 million copies worldwide. During this time period, Cyrus also released the song "Ready, Set, Don't Go", a collaboration with her father. It became her first Top 40 hit credited as herself, peaking at number 37 on the Billboard Hot 100. It also became her first Top 10 hit on the Hot Country Songs chart, peaking at number 4.
Shortly afterwards, Cyrus signed a four-album deal with Disney-owned Hollywood Records. On June 26, 2007 Cyrus released the double-disc album Hannah Montana 2: Meet Miley Cyrus. The first disc was the soundtrack to the second season of Hannah Montana, while the second disc served as Cyrus' debut studio album. The album debuted at number one on the Billboard 200 with first week sales of 326,000 copies. The album went on to be certified certified three times platinum by the Recording Industry Association of America. The album spawned the single "See You Again", which served as Cyrus' first single as a solo artist. The song quickly became a hit, and became her first Top 10 hit on the Billboard Hot 100 chart. It was eventually certified Platinum in the country, making it her first single to be RIAA certified. The single also had success in countries such as Australia and Canada, where it also peaked inside of the Top 10. The album's second single, "Start All Over", was released in early 2008. The single failed to match the success of its predecessor, debuting and peaking at number 68 on the Hot 100 chart. Numerous songs from the Hannah Montana portion of the album charted worldwide following its release.
During the fall of 2007, Cyrus launched the Best of Both Worlds Tour to promote the joint album. With the Jonas Brothers, Aly & AJ, and Everlife as her opening acts, Cyrus toured from October 17, 2007, to January 31, 2008, with stops in the U.S. and Canada. Tickets sold out in minutes and were scalped for up to $2,500 and an average of $214, well above their $26–$65 face value. A Ticketmaster official commented, "People who have been in this business for a long time are watching what's happening, and they say there hasn't been a demand of this level or intensity since The Beatles or Elvis." After the end of the Best of Both Worlds Tour in January 2008, Walt Disney Pictures released Hannah Montana & Miley Cyrus: Best of Both Worlds Concert, a 3D concert film of the tour, on February 1, 2008, for what was expected to be a one-week run.
On July 22, 2008, Cyrus released her second studio album under her own name, titled Breakout. Cyrus said Breakout was inspired by "what's been going on in my life in the past year." Cyrus co-wrote eight out of twelve songs on the album. "Songwriting is what I really want to do with my life forever, [...] I just hope this record showcases that, more than anything, I'm a writer." Breakout debuted at number one on the Billboard 200 with first week sales of 371,000 copies. This made it Cyrus' highest first week sales to date, and gave Cyrus her third number one album on the chart. The album went on to receive a Platinum certification from the RIAA, denoting sales of one million copies. Breakout was preceded by the lead single "7 Things", which became her second single to reach the Top 10 of the Billboard Hot 100. The album's second single, "Fly on the Wall", failed to have the same success, peaking at number 84 on the Hot 100. It was, however, successful in the United Kingdom, peaking at number 16 on the singles chart.
Both the film and its soundtrack, which contained twelve songs performed by Cyrus, achieved commercial success. The soundtrack's lead single, "The Climb", became a Top 40 hit in twelve countries and introduced Cyrus to listeners outside her typical teen pop audience. Cyrus had considered ending Hannah Montana after its third season, which finished production on June 5, 2009, but Disney retained and exercised its option for a fourth season. In September 2009, she participated in the charity single "Just Stand Up!" in support of the anti-cancer campaign Stand Up to Cancer and in the City of Hope Benefit Concert in support of cancer research and training programs. She also became involved in Disney's Friends for Change, an environmentalist group, for which she recorded the charity single "Send It On" along with several other Disney Channel stars. Shortly afterwards, Cyrus launched the third Hannah Montana soundtrack. The album debuted at number two on the Billboard 200, with first week sales of 137,000 copies. This was significantly lower than the first week sales for Cyrus' previous albums, and the soundtrack became her first to not receive an RIAA certification. The soundtrack did, however, spawn the single "He Could Be the One", which entered the Top 10 of the Hot 100.
In 2009, Cyrus launched her first clothing line with Max Azria, which was sold exclusively at Wal Mart. To promote the clothing line, Cyrus released her first extended play, The Time of Our Lives on August 31, 2009. Cyrus said The Time of Our Lives "is a transitioning album. [...] really to introduce people to what I want my next record to sound like and with time I will be able to do that a little more." The album debuted at number 3 on the Billboard 200, with first week sales of 62,000 copies. The following week, however, the album rose to number 2 on the chart, selling 153,000 copies. "Party in the U.S.A.", the album's lead single, debuted at number two on the Billboard Hot 100, making it her highest charting single to date. To promote the album, Cyrus embarked on the Wonder World Tour.
Her third studio album, Can't Be Tamed, was released on June 21, 2010. This would become her last album to be released through Hollywood Records. The album debuted at number 3 on the Billboard 200, with first week sales of 106,000 copies. This made it the lowest first week sales for one of Cyrus' studio albums, and her first studio album to not peak at number one on the Billboard 200 chart. The album only went on to sell a total of 343,000 copies in the United States to date, failing to receive an RIAA certification. The album was preceded by the lead single, "Can't Be Tamed". The single was released for sale on May 18, 2010, and peaked at number eight on the Billboard Hot 100. The album's second and final single, "Who Owns My Heart", was released only in select European countries. In February 2011, Cyrus confirmed she would be embarking on her Gypsy Heart Tour, which featured no North American dates. Cyrus later explained "Right now I just want to go to the places where I am getting the most love and Australia and South America have done that for me." The tour began in South America on April 29, 2011 and concluded on July 2 in Australia.
Cyrus announced plans to release her fourth studio album beginning in 2012. The album features production from various artists including Pharrell Williams and Hit-Boy. Billboard announced in January 2013 that Cyrus had signed with RCA Records, and also confirmed the album would be released in 2013. On March 5, 2013, it was announced that Cyrus had hired Larry Rudolph as her manager; Rudolph had previous worked with pop singer Britney Spears. Whilst working on the album, Cyrus appeared in various collaborations. She provided guest vocals for the Rock Mafia song "Morning Sun", and provided background vocals for the song "Decisions" by Borgore. Cyrus and Hemsworth later appeared in the music video for the song. Cyrus appeared on the Snoop Lion song "Ashtrays & Heartbreaks", released as a single for his Reincarnated album on April 4, 2013. She later appeared on the song "Fall Down", which was released as the fourth single for will.i.am's album #willpower on April 16, 2013. The single debuted at number 58 on the Billboard Hot 100, making it Cyrus' first single to chart on the Hot 100 since her 2010 single "Can't Be Tamed". The single also debuted inside the Top 20 in Canada, as well as the Top 40 in the UK. On May 23, it was confirmed that Cyrus would be featured on the Mike Will Made It single "23", alongside artists Wiz Khalifa and Juicy J. On June 3, Cyrus released "We Can't Stop", the lead single to her forthcoming album. Within 10 hours of its release, the song topped the iTunes singles charts in 30 countries, including the United States.
Before leaving to work on the film, Cyrus ended her nine-month relationship with model Justin Gaston. While filming later that month, Cyrus began dating her co-star in The Last Song, Australian actor Liam Hemsworth. She later called him her "first serious boyfriend". The couple started dating on April 23, 2011. Miley got engaged to boyfriend Liam Hemsworth on May 31, 2013 and got married on July 18, 2013.