No, Fermat’s theorem is not the hardest math problem in the world.
So let’s look deeper
No, Fermat’s theorem is not the hardest math problem in the world. While it was a famously difficult problem for a long time, it was eventually proven in the 1990s by Andrew Wiles. Since then, many other challenging math problems have emerged, some of which are still unsolved.
As stated by mathematician Marcus du Sautoy, “There are many famous problems out there in maths. Some are unsolved and still attract the attention of mathematicians around the world, while others have been solved in recent decades.” Here are some examples:

The Riemann Hypothesis: This is a conjecture regarding the distribution of prime numbers. It has remained unsolved since it was proposed in 1859 by Bernhard Riemann.

P vs. NP: This problem deals with determining whether or not certain problems can be solved quickly or efficiently. It has implications for many fields, including cryptography and computer science.

The Birch and SwinnertonDyer Conjecture: This relates to elliptic curves and their associated Lfunctions. While there has been progress made on this problem, it is still unsolved.

The Hodge Conjecture: This is a question in algebraic geometry that deals with the relationship between topology and geometry. It was proven in some special cases but remains unsolved in general.
These are just a few examples of math problems that are currently being studied by mathematicians around the world. As new ideas and techniques emerge, we may see progress made in these areas and others.
Math Problem  Brief Description  Status 

Riemann Hypothesis  Conjecture about prime number distribution  Unsolved 
P vs. NP  Question of efficient problem solving  Unsolved 
Birch and SwinnertonDyer Conjecture  Relates to elliptic curves and Lfunctions  Unsolved 
Hodge Conjecture  Relationship between topology and geometry  Proven in some cases, unsolved in general 
In conclusion, while Fermat’s theorem was a challenging problem, it has since been solved and other math problems have taken its place as some of the hardest and most interesting challenges in the field.
A visual response to the word “Is Fermat’s theorem the hardest math problem in the world?”
Fermat’s Last Theorem had been unsolved for 350 years, which stated that no solutions existed for an equation where X to the N plus Y to the N equals Z to the N when N is bigger than 2. Andrew Wiles was motivated to prove it, not for potential applications to cryptography, but to have his name on something that mathematicians have been trying to prove for centuries. With his solution, he opened up a new area of mathematics and allowed us to understand many new equations.
Some additional responses to your inquiry
It is among the most notable theorems in the history of mathematics and prior to its proof was in the Guinness Book of World Records as the "most difficult mathematical problem", in part because the theorem has the largest number of unsuccessful proofs.
Fermat’s Last Theorem is one of the most notable theorems in the history of mathematics and was once considered the "most difficult mathematical problem". It has the largest number of unsuccessful proofs. Along with the yet unproven Riemann’s hypothesis, Fermat’s Last Theorem is considered to be one of the hardest math problems in the world.
It is among the most notable theorems in the history of mathematics and prior to its proof was in the Guinness Book of World Records as the "most difficult mathematical problem", in part because the theorem has the largest number of unsuccessful proofs.
Fermat’s Last Theorem, along with the unsolved Riemann’s hypothesis is so far the worlds hardest math problem.
Along with the yet unproven Riemann’s hypothesis, Fermat’s last theorem is without doubt the hardest math problem in the world.
It is among the most notable theorems in the history of mathematics and prior to its proof was in the Guinness Book of World Records as the "most difficult mathematical problem", in part because the theorem has the largest number of unsuccessful proofs.
While I agree with Alan Bustany’s answer [ https://www.quora.com/WhatisthemostdifficultmathproblemeversolvedthatisnotFermatslasttheoremorPoincaresconjecture/answer/AlanBustany ] that “most difficult” is impossible to answer objectively, there are nonetheless a great many difficult mathematical theorems that probably should be mentioned.
For example, Ernie Cohen’s [ https://www.quora.com/WhatisthemostdifficultmathproblemeversolvedthatisnotFermatslasttheoremorPoincaresconjecture/answer/ErnieCohen1 ] example of the classification of finite simple groups is very good—that result was very important in group theory, and has been used to prove many more results since. It was a real triumph, as it took dozens of mathematicians working over fifty years to finally finish a complete proof. For those wondering what a finite simple group is, Alon Amit [ https://www.quora.com/Intuitivelywhatisafinitesimplegroup/answer/AlonAmit ] has a nice answer.
Perhap…
More intriguing questions on the topic
 The Poincaré Conjecture.
 The Prime Number Theorem.
 Fermat’s Last Theorem.
 The Reimann Hypothesis.
 Classification of Finite Simple Groups.
 Four Color Theorem.
 Goldbach’s Conjecture.
 Inscribed Square Problem.