See Scottish Kings and Queens 

Saint Andrew and The Saltire -The National Flag of Scotland

St. Andrew was one of the first Disciples of Christ. He was a missionary to Asia Minor and Greece and was crucified by the Romans on an x-shaped cross at Patras in 69 AD. 
His remains were entombed and in 370 AD were taken from Constantinople to a Pictish settlement on the Eastern Coast of Scotland where nowadays the city of St. Andrews is. 

In 832 AD a Pictish army led by King Angus Mac Fergus, King of Alba and another army under Eochaidh, King of Dalriada were fighting a Northumbrian force in Lothian. The winner would have the control of that area. 

The night before the battle Angus saw St. Andrew in his dream so, the king prayed for victory and miraculously, the following day, the same vision appeared in the sky in the form of a Saltire or x-shaped cross. It is said that the Picts and Scots made the Northumbrians run away when their leader Athelstan was killed in the battlefield. The site of the battle is known as Athelstanford. 

The colours of the flag represent the blue sky and the white clouds. From that moment onwards, the Saltire became the national emblem of the Scots and it was not only used as a flag but also worn on bonnets and tunics. 

In 1707 Scotland and England joined in the Act of Union and they became the United Kingdom, as England had its own flag, the one bearing St. George's cross and Scotland had its own, there was great confusion, in other words, nobody knew what flag to use and when; therefore, a new flag representing this union was designed bearing the Crosses of St. Andrew (Patron of Scotland) and St. George (Patron of England) and later, the cross of St. Patrick (Patron of Ireland) was added.
The flag of this union is commonly known as "The Union Jack" which is the flag that represents the United Kingdom of Great Britain and Northern Ireland today.

The Royal Flag of Scotland

There is a second flag associated with Scotland "The Rampant Lion" or "Royal Flag of Scotland". Nowadays, only Royalty uses this flag. 

King George V signed a Royal Warrant in 1934 allowing the use of the Rampant Lion. The Lord Lyon king of Arms is the judicial officer who grants official permission to fly this flag.
The lion was used by many Scottish kings for centuries. Some believe that perhaps the Scottish kings kept a real lion when residing at Stirling and Edinburgh Castles. Both castles have a building within their walls known as The Lions' Den.

Copyright Monica Loreto

Saltire

Royal Flag

Union Jack

Scottish version of the  Union Jack