Justin Timberlake recently landed himself in hot water following a tweet he posted describing Madonna as "his ninja."

On Saturday, many celebrities including Justin Timberlake wished the legendary singer a happy 56th birthday. However, Timberlake's tweet sparked controversy among fans that were offended by Timberlake's use of the word ninja.

According to Hip Hop Wired, ninja is often used as a "visual and auditory safe substitute for the n-word."

Timberlake's tweet read, "A happiest of Bdays to my mother chucking ninja, @Madonna!! Hope you have a great one, M!"

Following Timberlake's birthday tweet to Madonna, Twitter users slammed the "Suit and Tie" singer for his choice of phrase.

Immediately after posting the tweet, Timberlake deleted the post from his account.

However, the damage was already done.

In addition to social media users, media outlets also slammed the 33-year-old singer.

The Hot Hits reported on Timberlake's ninja tweet story and later commented, "Before you shout out, 'BUT HE SAID NINJA! STOP OVERREACTING!' you should know it's not uncommon in America for those who think they're smart to use 'ninja' in place of the other word, as the Twitter users...have caught."

The Hot Hits then added, "When will people learn that no matter what the situation is, it is never okay to use, nor imply discriminatory and racial slurs like that?"

Us Weekly reports Timberlake isn't the only celebrity that has used ninja as a replacement for the n-word. In 2012, Katy Perry sang a cover of Kanye West and Jay-Z's song, "N*gg*s in Paris." Instead of using the n-word, she substituted the word ninja.

Madonna was also slammed back in January for referring to her adopted African-American son as "dis n*gg*" on Instagram, The Blemish a.

Madonna later issued an apology for her racial slur.

Did Justin Timberlake take it too far by referring to Madonna as his ninja? Share your comments below.