Hey everyone,
I can guess the Swordsman, or something similar to it, has already been posted 1.000~ish times before, but I hope I did it some justice.
This is my very first subclass homebrew. I hope I have not overpowered this subclass which is why I have posted it here, to kindly ask for your feedback on it.

Well here goes nothing:

Swordsman (Fighter Subclass)

Level 3: Trained Reflexes.
Intense training with a variety of blades has taught you to wield your weapon to a remarkable level.
While you wield no shield nor wear any heavy or medium armour and while wielding a single Longsword, Short-sword, Scimitar, Rapier or Dagger, you are granted the following abilities:

Intense Weapon Training.
Your harsh training with blades makes you a formidable opponent in combat.
You are allowed to add 1d4 to your attack and damage-rolls made with one of the aforementioned weapons.
This bonus is improved to 1d6 on level 7, and improved further to 1d8 on level 14.
You can use this ability an amount of times equal to your proficiency bonus before requiring a Short-rest to regain all uses.

Missile Deflection.
Your training has made you capable of slicing incoming projectiles out of the air before they strike you.
When you are the target of a ranged-attack, you can use your reaction to gain +4 AC against all ranged attacks and spell-attack rolls that target you on this turn.

Level 7: Thoughts Calm Like a Gentle Breeze.
Your training has not only sharpened your blade, but also your mind and body.
Being surprised does not grant your attacker(s) advantage on their attack against you.
You can spend one use of your second-wind to grant yourself advantage on Wisdom and Intelligence saving-throws imposed onto you by magical sources.
You gain advantage on all Charisma-based ability checks and saving-throws during conversation.
You gain 5ft. of movement speed.

Level 10: An Extension of the Body.
You have become used to wielding blades to the point that it feels like they have become a weightless extension of your body. Not having your blade by your side would leave you with an uncomfortable feeling, as if you are missing a part of your body.
You are allowed to take the Dash-action as a bonus-action instead.
As a bonus action, you can perform a single melee-attack provided you use one of the aforementioned weapons above. The attack made with this ability can still benefit from the "Intense Weapon Training" bonus.

Intercepting Grapple.
When you are the target of a melee attack, made by a creature no more than 1 size larger than you. you can choose to roll a DEX or STR saving-throw (player's choice) with the DC being the attacker's attack-roll.
Upon failure you take damage as normal. Upon succeeding the saving-throw, you take no damage from the attack and successfully catch the weapon before it strikes you. The target who initially attacked you is at this point considered "grappled" and cannot use this weapon to attack again, until the grapple ends.

Level 15: Cutting Strikes.
Through intense training and focus, you have made another cutting-edge discovery in your mastery over the blade. Additionally you have learned how to perform a cutting strike with your bare hands.
Your unarmed strikes are now able to benefit from the "Intense Weapon Training" ability and will deal Slashing damage instead when chosen to do so.
When you choose to attack a target in melee, after having travelled at least 40ft using the Dash bonus-action, you may double the bonus dice gained from the "Intense Weapon Training" ability (2d8), for the duration of this turn.

Level 18: Cutting Winds.
By surviving all deadly trials and overcoming all obstacles laid upon you, during your adventures, has honed your skills to a sharpness unseen before. You have fully mastered the ability to cut, in it's purest form.
Your attacks with any of the aforementioned weapons (including your unarmed strikes with the "Cutting Strikes" ability) grant you an attack-range of 20ft. as you project your slashes through the air at range. These attacks use your normal melee attack-rolls and can benefit from the "Intense Weapon Training" and the "Cutting Strikes" ability, but can still target only a single target.

I hope you all enjoyed reading this as much as I enjoyed creating this! I'm looking forward to everyone's feedback and I'm willing to modify this accordingly to make sure this can become balanced enough to see actual-play in other people's games! 

(while creating this i simply couldn't rid my mind of the fedora-tipping neckbeard stereotype joke...) xD

Light armored, (mostly) finesse weapons, extra damage on a hit, damage mitigation/avoidance reaction, charisma boost in conversation, dash as a bonus action...

You made a Swashbuckler Rogue :)

Seriously though, these features overlap pretty heavily with other classes. When you make a fighter subclass, you need to really feel out what it means to be a fighter and how this subclass is going to enhance that. As written, this feels much more appropriate as a rogue or maybe a bard.

But if we're going with fighter, consider the math of the game. Attacks vs AC boils down to math. Rogues even the math with Evasion and Uncanny Dodge, Barbarians do it with Unarmored Defense and damage resistance, Fighters do it with armor. Forcing a fighter into light armor/no shield without anything to rebalance the math is going to tank the survivability of this subclass. He can (maybe) deflect a ranged attack, but at the cost of a Reaction which is important for a melee class.

And the other side of the coin is attack/damage. You give a damage bonus, but any fighter could get a similar or better damage bonus by just dual wielding. I'm not sure the benefits granted at level 3 even outweigh the restrictions that they come with, much less grant a competitive advantage over other subclass choices at that level.

Overall, I'd probably redo this as a subclass of another class.

I agree with the above this is just a Kensei Monk but you are technically a fighter.