Goulding's debut album Lights was released in March 2010, reaching No. 1 on the UK Albums Chart and No. 6 on the Irish Albums Chart. Its singles "Starry Eyed", "Guns and Horses", and "The Writer" peaked at Nos. 4, 26, and 19. As of June 2012, the album had sold over 850,000 copies in the UK and 1.6 million copies worldwide. In August 2010, she released a second EP, Run into the Light, containing remixes of songs from Lights. The album was supported by Nike and was released through Polydor as a running soundtrack in an effort to get her music taken up by the running subculture. In November 2010, Lights was re-released as Bright Lights, with six new tracks added. It was originally announced that the lead single from Bright Lights would be the new edit of the title track with a release scheduled for 1 November 2010. This plan was ultimately scrapped to allow her cover of Elton John's "Your Song" to be released in conjunction with the John Lewis Christmas advert in the UK in 2010. The single became her second highest-charting single to date, reaching No. 2 on the UK Singles Chart. It also charted in some European countries. In January 2011, it was announced that the title track from Lights would serve as the second single from Bright Lights. "Lights" reached No. 49 on the UK Singles Chart, while becoming Goulding's first song to chart in the United States, as well as her highest-charting song to date, peaking at No. 2 on the Billboard Hot 100 in August 2012.
Goulding toured in support of Lights and supported Passion Pit in March 2010 and John Mayer during his British tour in May 2010. During the summer she performed at a number of festivals. On 29 May she performed at the Dot to Dot Festival in Bristol. She performed a set on 25 June at the Glastonbury Festival 2010 on the John Peel Stage. Her third EP was a live recording of part of her set at the iTunes Festival 2010. The whole set was ultimately included as bonus content on the iTunes version of Bright Lights. She made her T in the Park debut on 11 July. In early 2011, she recorded an original song for the film Life in a Day. Ellie Goulding was No. 5 on Rolling Stone's annual hot list in February 2011. In February 2011, she returned to the Brit Awards where she was nominated for Best British Female and Best British Breakthrough Act but lost out to Laura Marling and to Tinie Tempah.
Goulding's debut album Lights (2010) experimented with genres including indie pop, synthpop, folktronica and indietronica. The album contained "sparkling pop with a folky heart and an electronic edge" and was noted as being infectious. The album incorporated "acoustic guitar" and "retro-synthpop" compared to that of Little Boots and La Roux, while the production contained "folkie origins under a welter of busily cycling synths and programmed beats". Goulding toured the United Kingdom with American folk singer Lissie in 2010. Goulding's second album Halcyon followed in the same vein, including genres such as indie pop, synthpop and dream pop. She stepped away from the electronic sound of her previous album and moved to a more tribal and anthemic sound containing a bit more piano and vocal.
She dated English radio DJ Greg James in 2010. Their relationship ended in 2012 after 18 months together. In the same year, after collaborating on a song called "Bittersweet" for the Twilight: Breaking Dawn Part Two soundtrack, Goulding started dating DJ Skrillex. The two split nine months later, citing the long distance nature of their relationship. Goulding later was in a relationship with actor Jeremy Irvine. They broke up in August 2013. Goulding was in a relationship with Dougie Poynter of McFly between 2014 and 2016. On 7 August 2018, Goulding and her boyfriend Caspar Jopling announced their engagement. The couple were married at York Minster on 31 August 2019 and Goulding was baptised in order to get married. Jopling is the grandson of former Conservative MP Michael Jopling, who was the Minister of Agriculture, Fisheries and Food from 1983 to 1987.
Goulding contributed her vocals to an advert for the British department store chain John Lewis in 2010. The John Lewis Christmas advert has become an annual tradition in British culture and one of the signals that the countdown to Christmas has begun in the UK, with Goulding performing "Your Song" for the store's 2010 campaign.
In 2010, Goulding participated in the Bupa Great North Run for the British Heart Foundation. In 2011, Goulding ran the She Runs LA event for charity Students Run LA, which aims to increase access to sport for less privileged children across the Los Angeles Unified School District.