<P> Pretty Little Liars is a TV series which premiered on ABC Family on June 8, 2010 . Developed by I. Marlene King, the series is based on the Pretty Little Liars book series by Sara Shepard . The series follows the lives of four girls, Aria Montgomery, Hanna Marin, Emily Fields, and Spencer Hastings, whose clique falls apart after the disappearance of their leader, Alison DiLaurentis . One year later, the estranged friends are reunited as they begin receiving messages from a mysterious figure named "A" who threatens to expose their deepest secrets, including ones they thought only Alison knew . </P> <P> After an initial order of 10 episodes, ABC Family ordered an additional 12 episodes for season one on June 28, 2010 . The first season's "summer finale" aired on August 10, 2010, with the remaining 12 episodes began airing on January 3, 2011 . On January 11, 2011, ABC Family picked up Pretty Little Liars for a second season of 24 episodes . It began airing on Tuesday, June 14, 2011 . It was announced in June that a special Halloween - themed episode would air as part of ABC Family's 13 Nights of Halloween line - up . This increased the episode count from 24 to 25 . On November 29, 2011, ABC Family renewed the series for a third season, consisting of 24 episodes . On October 4, 2012, ABC Family renewed the series for a fourth season, consisting of 24 episodes . On March 26, 2013, ABC Family renewed the series for a fifth season . On January 7, 2014, showrunner I. Marlene King wrote on Twitter that season 5 will have 25 episodes, including a holiday - themed episode . On June 10, 2014, it was announced that the show was renewed for an additional 2 seasons . Season 6 will air in mid-2015, and season 7 will air in mid-2016 . It was announced by I. Marlene King that the sixth and the seventh season will consist of 20 episodes each . It was announced on August 29, 2016, that the show would be ending after the seventh season, and that the second half of the season would begin airing April 18, 2017 . </P> <P> As of June 27, 2017, 160 episodes of Pretty Little Liars have aired, concluding the series . </P> <Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th_colspan="2"> Nielsen ratings </Th> </Tr> <Tr> <Th> First aired </Th> <Th> Last aired </Th> <Th> Viewers (in millions) </Th> <Th> Adults (18 - 49) </Th> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 22 </Td> <Td_colspan="1"> June 8, 2010 (2010 - 06 - 08) </Td> <Td> March 21, 2011 (2011 - 03 - 21) </Td> <Td> 2.87 </Td> <Td> 1.0 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 25 </Td> <Td_colspan="1"> June 14, 2011 (2011 - 06 - 14) </Td> <Td> March 19, 2012 (2012 - 03 - 19) </Td> <Td> 2.68 </Td> <Td> 1.0 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> June 5, 2012 (2012 - 06 - 05) </Td> <Td> March 19, 2013 (2013 - 03 - 19) </Td> <Td> 2.59 </Td> <Td> 1.1 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> June 11, 2013 (2013 - 06 - 11) </Td> <Td> March 18, 2014 (2014 - 03 - 18) </Td> <Td> 2.53 </Td> <Td> 1.1 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 5 </Td> <Td_colspan="2"> 25 </Td> <Td_colspan="1"> June 10, 2014 (2014 - 06 - 10) </Td> <Td> March 24, 2015 (2015 - 03 - 24) </Td> <Td> 2.01 </Td> <Td> 0.9 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 6 </Td> <Td_colspan="2"> 20 </Td> <Td_colspan="1"> June 2, 2015 (2015 - 06 - 02) </Td> <Td> March 15, 2016 (2016 - 03 - 15) </Td> <Td> 1.72 </Td> <Td> 0.8 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 7 </Td> <Td_colspan="2"> 20 </Td> <Td_colspan="1"> June 21, 2016 (2016 - 06 - 21) </Td> <Td> June 27, 2017 (2017 - 06 - 27) </Td> <Td> 1.11 </Td> <Td> 0.6 </Td> </Tr> </Table>

When was the last episode of pretty little liars aired