Expert Difficulty

 is one of the track difficulties the player can challenge in the Bloons Tower Defense Games. Expert Difficulty is the second hardest difficulty, with Extreme Difficulty being the hardest. This difficulty was introduced in Bloons TD 4 and it is the highest track difficulty in Bloons TD 4 and Bloons TD 4 Expansion. It is the highest track difficulty in Bloons TD 6 as well.

In Bloons TD 5, it is the second hardest difficulty, because Extreme Difficulty is higher. Expert tracks usually have to be unlocked by reaching a certain Rank (28 for Clock, 34 for Castle, 40 for Death Valley, 41 for Drag Strip, 43 for Tree Tops).

In BTD6, it is the hardest difficulty in the game. Each Expert Map requires a certain number of Advanced Maps completed with at least Easy Difficulty completed. Expert Maps typically take highly extensive measures onto all aspects of the game, particularly in regards to Line of Sight or incorporating multiple lanes. Certain Expert Maps such as Workshop also feature elements that are normally considered too complicated for Advanced, although some players consider certain Advanced Maps to fit under the same criteria for Expert, such as the case for Geared (an Advanced Map).

This difficulty tends to be easier than the Extreme Difficulty (though to some, Expert Maps are harder than them), however these tracks are still a challenge on harder difficulties.

Bloons TD 6
The Expert Difficulty Maps in Bloons TD 6 are:
 * Muddy Puddles
 * #Ouch
 * Dark Castle
 * Quad
 * Workshop
 * Bloody Puddles
 * Infernal
 * Flooded Valley
 * Ravine
 * Sanctuary
 * Blons

Most of these maps are known to be notoriously difficult, and many attempts at C.H.I.M.P.S. have required the use of specific tower placements, powerful towers, and community effort.

Special Missions used in BTD5 and BTD5 Deluxe

 * Fast Upgrades (BTD5, Castle)

BTD5
The Expert Difficulty tracks in Bloons TD 5 are:
 * Clock
 * Castle
 * Death Valley
 * Drag Strip
 * Tunnels
 * Tree Tops
 * Runway
 * Down the Drain
 * Spooky Castle
 * Dark Forest
 * Spider Map (Co-op Mode only)

BTD5 Deluxe
There are two new Expert tracks in Deluxe:
 * Ascension
 * Railway Track

BTD5 iOS
There are four new Expert tracks on Mobile/Steam:
 * Double Double Cross
 * Benguela
 * Web
 * Forest Path