Mr Weir had been an MLA since 1998 when the Assembly was first created following the Good Friday Agreement.
The DUP previously held three seats in the constituency - but was always likely to struggle to hold them all. However Mr Weir was the casualty.
In a heartfelt post on his Facebook page, Peter Weir wrote: "Although i wasn’t successful today, I want to place on record my grateful thanks for all those who voted for me, and indeed all those who took part in the democratic process.
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"I especially want to thank my team, of whom i am immensely proud.
"A more dedicated and better bunch i could not hope to meet, it has been a privilege to serve."