Air-time legends: The longest-running TV series ever - 'Grey's Anatomy' has just had its 15th season confirmed by ABC, reports Cosmopolitan. But is that too long for a TV show? Definitely not! There are many more TV shows that have run for just as long, if not longer (and we're not talking about soaps)! Did you know that 'The Simpsons' has been on air for almost 30 years, for example? Or that 'Law & Order,' which became a massive franchise, aired for two decades?

Check out which are the longest-running TV series in the world!

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'Grey's Anatomy' - Everyone was expecting 'Grey's Anatomy' to run for another season, and after the recent announcement by ABC, it's now confirmed! Ellen Pompeo already renewed her contract with the channel in January this year, according to The Hollywood Reporter.

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'Grey's Anatomy' - The series, masterminded by Shonda Rhimes, has won the record for being the longest-running drama on prime time TV ever, according to Cosmopolitan.

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'Grey's Anatomy' - The character of Meredith Grey thrust actress Ellen Pompeo into the world's spotlight, and has since made her the best-paid TV actress. She now earns US$575,000 per episode, which equates to approximately US$20 million per year, according to The Hollywood Reporter. Not bad!

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'Law & Order' - Number of seasons: 20 
The story follows police investigations and the fight for justice in the city of New York. The show first aired in 1990 and features 456 episodes.

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'Law & Order' - Before making a name for himself as Mr. Big on 'Sex and The City,' Chris Noth played detective Mike Logan. His character even made a return to the screen in 'Law & Order: Criminal Intent.'

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'Law & Order: SVU' -

Number of seasons: 19 
The show has a loyal following and launched Mariska Hargitay, who plays the feisty detective Olivia Benson, into TV stardom.

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'Law & Order: SVU' - First aired in 1999, the series came out of the original 'Law & Order' and has almost overtaken it in terms of longevity.

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'NCIS' - Number of seasons: 15 
Starring Mark Harmon, the series was also a big hit on American TV, and has just had its 16th season confirmed by CBS, reveals The Hollywood Reporter. It aired for the first time in 2003 and has run for over 344 episodes.

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'NCIS' - The show follows a group of special agents whose mission is to investigate any crime relating to the Navy or its officers.

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'Sesame Street' - Number of seasons: 48 
'Sesame Street' wins the prize for the series that has been on air the longest! The kids show, which first aired in 1969, features over 4,491 episodes.

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'Sesame Street' - And not only is it the longest-running show, it's also one of the most awarded, with 167 Emmys to its name.

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'The Simpsons' - Number of seasons: 29 
When 'The Simpsons' first aired over three decades ago, no one could have imagined that the yellow family of five would have such a huge impact on American TV. Today, Homer, Marge, Bart, Lisa, and Maggie are still going strong and have confirmed their 30th season!

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'The Simpsons' - The show, which has run for 637 episodes so far, is a real pop culture brand. It's won loyal TV followers and 30 Emmys since it first aired.

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'South Park' - Number of seasons: 21
The animated satire show, which aired for the first time in 1997, has been another huge TV hit.

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'South Park' - 'South Park' has won five Emmys for Outstanding Animated Program and has a further two seasons confirmed, with the 23rd having just been guaranteed this year.

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'Doctor Who' - Number of seasons: 37
The series was first released in 1963. In 2018, the cult show entered a new era with the role of the doctor being played by a woman, Jodie Whittaker, for the very first time.

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'Doctor Who' - The series, whose last male doctor was played by Peter Capaldi, has gone down in the Guinness World Records as the longest-running science fiction TV series in the world.

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'ER' - Number of seasons: 15 
The 331-episode show was responsible for the increasing popularity of medical TV series.

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'ER' - On air from 1994 to 2009, the series starred none other than Hollywood giant George Clooney, as well as Julianna Margulies and Noah Wyle, who later went on to appear in 'The Good Wife' and 'Falling Skies,' respectively.

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'Family Guy' - Number of seasons: 16 
The sitcom created by Seth MacFarlane made its debut in 1999 and is still running today.

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'Family Guy' - The show actually stopped in 2002, but because of huge sales of DVDs it returned to the air in 2005.

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'CSI: Crime Scene Investigation' - Number of seasons: 15 
The police series was so successful that it led to other spin-offs, including 'CSI: Miami,' 'CSI:NY,' and 'CSI: Cyber.'

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'CSI: Crime Scene Investigation'' - The crime drama first aired in 2000 and ended in 2015. Because it wasn't renewed for another season, it had its finale in a TV movie that was also released in 2015.

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'Grange Hill' - Number of seasons: 31 
The British TV series, which followed the story of life in a comprehensive school, finally ended in 2008 after running for 601 episodes. It won the BAFTA for Best Children's Programme four times (in 1979, 1980, 1986, and 2001).

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'Gunsmoke' - Number of seasons: 20
The Western drama series, which starred James Arness (pictured) and Milburn Stone (who won an Emmy for her performance), ran for a total of 635 episodes.

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'Last of The Summer Wine' - Number of seasons: 31
The British BBC sitcom ran for 295 episodes, from 1973 to 2010.

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'Death Valley Days' - Number of seasons: 18
Did you know that before he became the US President, Ronald Reagan used to be an actor? Well, now you can watch him act in this series.

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'Death Valley Days' - Curiously, the show actually started out on radio, in 1930, before switching to TV for 18 years. There were 451 episodes produced.

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'Bonanza' - Number of seasons: 14
The Western saga aired between 1959 and 1973, totaling 430 episodes.

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'Bonanza' - The series told the story of widowed rancher Ben Cartwright (Lorne Greene), and his three sons (from different mothers), who fight to run their ranch, Ponderosa, in Nevada.

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