The former Broxburn Academy pupil was awarded the sought-after award at the Celtic Connections festival in Glasgow recently.
She was one of five finalists performing live for the top award, and was unanimously chosen by the judges as the overall winner.
This is another milestone in Hannah's promising musical career, which has included touring America and performing live on the BBC's Hogmanay show.
Broxburn Academy Head Teacher Peter Reid said: "Huge congratulations to Hannah on achieving this fantastic award.
"Hannah is an inspiration to our students, showing what can be achieved through talent, hard work and determination.
"She is remembered very fondly by the whole Broxburn Academy community from her time here, and everyone follows her journey of success. It's fantastic to see a pupil go from starring in our schools shows to award-winning professional musician.
"Hannah still comes back to support our school shows and concerts every year, which will help motivate our current pupils to achieve the full potential."
Dave King, executive councillor for culture and leisure, added: "It's fantastic to see a gifted West Lothian musician pick up a top national award like this.
"West Lothian can be rightly proud of Hannah Rarity's achievement, and I'm sure she will enjoy a long and successful music career."
Singer Hannah Rarity wins BBC Radio Scotland Young Traditional Musician 2018
Footage and live performances from the finals, can be seen at BBC Young Trad