The Lion Is the National Animal of the United Kingdom

The original answer contained a contradiction. Clarified: The lion IS the national animal of the United Kingdom.

Symbolic Role

• Royal Arms: Lion rampant (Scotland) and lion passant guardant (England) — combined in UK coat of arms
• Heraldry: Three lions passant guardant (England) since Richard I (1198); red lion rampant (Scotland) since William I (1165)
• British Army: Cap badge of Royal Regiment of Fusiliers, Royal Tank Regiment, others
• National teams: England cricket, football (Three Lions); Scotland rugby (Thistle + Lion)
• Currency: £1 coin (pre-2017) featured three lions; current £1 has nations' floral emblems

Why the Lion?

Medieval English kings adopted the lion as personal emblem (Henry I, Henry II, Richard I "Lionheart"). It represented courage, sovereignty, and Christological symbolism (Lion of Judah). Scotland independently adopted the rampant lion. The 1707 Union combined both in the Royal Arms.

Not the Only Symbol

• Unicorn: Scotland's supporter in Royal Arms (chained — "untamable")
• Bulldog: Informal national personification (Churchill era)
• Rose / Thistle / Shamrock / Daffodil: Floral emblems of England, Scotland, NI, Wales

The lion remains the primary zoomorphic national symbol — heraldically, historically, and popularly.