Any character can replace their Attack Action to try and Shove an enemy in melee range using a contested Athletics check. A character with more than one Attack can substitute a Shove for one Attack. If the attacker fails they lose nothing but the Attack. If they succeed, the enemy either falls Prone or moves back 5 feet.

Why don't all Str-based martial characters use this more? I can see not trying to shove a giant or an Ogre but a Fighter with 3 attacks and GWM can shove the enemy to the ground and then get 2 attacks at Advantage. Anyone else in the party who gets to act before the bad guy can stand can also make melee attacks at Advantage.

Why don't players use this more?

To Shove a creature cost an attack and is somewhat situational, most player character prefer to attack a target rather tha knock it prone or push it 5 feet away unless there is an area of effect or other hazard detrimental to it, or an advantage to multiple attacks by the shover & allies.

Yeah, mostly Shove doesn't really do damage, so it tends to lose out in the choice between making an enemy more dead and....not doing that. 

In addition to the above, it gives any ranged characters in the party disadvantage. Depending on party composition, you may hurt more allies than you help. 

In a Party of two or more melee PCs, I always recommend knocking opponents prone to gain advantage on attacks. Is it optimal? I don't know. But is it fun to knock someone down so everyone can beat the shit out of them? Absolutely!

At standard 70% hit rates, sacrificing an attack to gain advantage on subsequent attacks pays off in 3.3 additional attacks. Given that shove can fail, it generally takes 4-5 attacks to actually pay off. Given that the advantage is melee only and the target can stand up on his next action, this is rarely worth doing, though it can pay off in special cases.

Quote from Pantagruel666 >>

At standard 70% hit rates, sacrificing an attack to gain advantage on subsequent attacks pays off in 3.3 additional attacks. Given that shove can fail, it generally takes 4-5 attacks to actually pay off. Given that the advantage is melee only and the target can stand up on his next action, this is rarely worth doing, though it can pay off in special cases.

I think day-to-day, knocking opponents prone is fun, but not optimal. However, in the special cases you mention, it can be great. Fighters using Action Surge and/or being Hasted can really help land the blows and crits. Also, if someone has a way, say Silvery Barbs, to help the melee PC succeed in knocking someone prone, then the value continues to go up.

In my current campaign, we have two fighters, a ranger (who prefers melee combat), and a wizard. They are absolutely going to wreck bad guys when they hit level 5. Not in every circumstance, of course, but there will be days where it's just glorious!

It's one of those options a lot of people don't really consider unless a skill modifies it. 

(For example, I never used the Help action much until I started playing a fae hobgoblin who can use it as a bonus action with new effects.) 

Quote from mtngoatjoe >>

I think day-to-day, knocking opponents prone is fun, but not optimal. However, in the special cases you mention, it can be great. Fighters using Action Surge and/or being Hasted can really help land the blows and crits.

 Yeah, if you're not playing a battlemaster (in which case you just take trip attack) one of the classic 'likely to be useful' is on your first attack when you have 2+ attacks and plan on using action surge. Though if you're a fighter who plans on doing a lot of shoving, shield master is definitely worth consideration.

I've never had an all-melee party, so shoving always hurt at least one ally as much as it helped another. It's a useful tool to have in certain situations - just like grapple - but not a primary tactic.

Fair points, all. My current party has more melee than most I think and even the ranged fighters have melee options. We also have two with GWM so the Advantage makes for big damage rounds even against opponents with higher AC.

I wish shove was more effective, but then again I have a weakness for playing low-strength characters.

One of the problems that keeps shoving from being used much is that 5E has a rocket-tag gameplay style: damage output is high compared to enemy HP so it doesn't take a huge amount of hits to down an enemy.  Consequently, any action that isn't damaging the enemy is a less-useful action.

It's a quite tactical decision to use shove, heavily depending on Initiative order. Mostly useful to knock a target prone, except when you can push it off a high place or into some hazard. But the opportunities where this is viable are too rare most of the times to forgo dealing "normal" damage.

Hm. I've never considered this, but maybe barbarians should be shoving opponents all the time. After all, it's a strength check, on which they have advantage. Right? Or is it only pure strength, and not Athletics?

Regardless, some fun could be had with this, particularly if you shove someone like ... a caster. Advantage also means double crit chance, so that's not nothing. 

Also worth noting the benefits of combining Armorer Artificer with Fighter for using Shove.

Make a high int, decent strength character and then use Armour of Magical Strength. Assuming +4 and +3, and proficiency in Athletics, you can end up with around +10 on the roll for shoving, with 6 charges. A higher level character building towards this could have +5/+4 with +4 prof and a dip into rogue for expertise could be shoving with +17 on the roll and then sneak attack damage for having advantage thereafter!

...daym...

Ok, just made a silly lvl 8 build but could be effective!

Artificer 7, rogue 1.
2 finesse weapons
Stealth model armour
Armour of magical strength
Expertise in Athletics
Str 16, Int 20, Dex at least 13

First attack, shove. Expertise plus strength gives +9. Armour of strength to give +5 (int), use reaction to use flash of genius to give +5 (int) again, for a total of +19 to the shove roll.

Second and offhand attack, stab them while they're down, get sneak attack damage and advantage.

When you hit level 9 that goes to +21 as prof. bonus goes up. Take levels in rogue, at level 10 you get 2d6 sneak attack dice.

Consider instead branching into rune knight for becoming large (allowing you to shove huge creatures). Use enlarge/reduce (Artificer spell) to become Huge.

As Artificer 7, rogue 1, and fighter 3, you will be level 11, with

Expertise plus strength gives +11. Armour of strength to give +5 (int), use reaction to use flash of genius to give +5 (int) again, Rune knight gives advantage (approx +5), for approx. +26 (+21, plus advantage) on the roll, and you can push over Gargantuan creatures, like the Tarrasque. Then you can stab them a bunch, with bonus damage, and action surge to stab them 3 more times - yay!

-Edit - also noticed that Legendary Resistances help with saves, not contested rolls. So the Tarrasque would have a flat +10 on their roll, and you would have +21 with advantage. Using action surge, you can do this in one round - bonus to giants might, action to enlarge to huge, action surge to attack and shove (reaction to use flash of genius). Yes, it's all your economy in one hit, but it's a big hit!

Yep, shoving is underrated XD

Between 1-4, which a significant portions of game happens to be, characters can only attack once for the most part, so they rarely sacrifice their only attack to shove someone even if allies can gain an advantage, especially if other allies get disadvantage as well.

Past level 5+ you see a slkight increase of the use of shove or grapple, especially to lock down an enemy or push it off a ledge or into detrimental area.

From experience it's rarely used unless a character has invested in a build to enhance these tactics, i've either rarely seen it ever get used or get used a lot from a character specialized in it via feat and feature.

Quote from Metamongoose >>

Yeah, mostly Shove doesn't really do damage, so it tends to lose out in the choice between making an enemy more dead and....not doing that. 

 That needs to change. If you shove someone on the ground, it ought to do a little damage, and enable the next attack to be at advantage. As a DM, that's how I'd rule it. But again, both as a player and DM, rarely ever see it.

Quote from TheCosmicHand >>

Quote from Metamongoose >>

Yeah, mostly Shove doesn't really do damage, so it tends to lose out in the choice between making an enemy more dead and....not doing that. 

 That needs to change. If you shove someone on the ground, it ought to do a little damage, and enable the next attack to be at advantage. As a DM, that's how I'd rule it. But again, both as a player and DM, rarely ever see it.

When you attack a prone enemy, you get advantage for melee and disadvantage for ranged attacks, so you already do get the next melee attack at advantage, as well as every melee attack until they get up!

Use polearm master & sentinel to stop them getting up every time too - that'll do them over double time!