LocalPlayer is a read-only property which refers to the Player whose client is running the game.

This property is only defined for LocalScripts (and ModuleScripts required by them), as they run on the client. For the server (on which Script objects run their code), this property is nil. See articles/Roblox Client-Server Model for more information on game networking on Roblox.

This property is useful in LocalScripts which display information about the player viewing a GUI. Using For example, if there were IntValue parented to a Player named “Coins” which represented how much money that player has, you could use the following to display this value for them:

-- This code is appropriate for a LocalScript in StarterGui,
-- for example: game.StarterGui.ScreenGui.TextLabel.LocalScript

local player = game:GetService("Players").LocalPlayer
-- Wait for a value we're expecting for the server to have created
local vCoins = player:WaitForChild("Coins")

local textLabel = script.Parent
local function update()
    textLabel.Text = "Coins: " .. vCoins.Value
end

-- Update once, then every time the value changes
update()
vCoins.Changed:Connect(update)

Loading GUIs

When creating loading GUIs using ReplicatedFirst, sometimes a LocalScript can run before the LocalPlayer is available. In this case, you should yield until it becomes available by using Instance/GetPropertyChangedSignal

local Players = game:GetService("Players")
-- Below: access Players.LocalPlayer; if it is nil, we'll wait for it using GetPropertyChangedSignal.
local player = Players.LocalPlayer or Players:GetPropertyChangedSignal("LocalPlayer"):wait()

Doing this isn’t for a LocalScript within StarterGui, StarterPlayerScripts or StarterCharacterScripts: these scripts can only run after a Player object is already available, and LocalPlayer will have been set by then.