Terence Crawford speaking to Showtime: "You always got a little butterflies, but I have been waiting for this moment my whole life. I'm ready for everything that comes with it. I'm focused on nothing but the victory right now and the things I got to do to secure the victory."

Here we go! Ring walk time.

The nerves are a'tingling in anticipation now.

Errol Spence speaking to the Showtime: "I'm excited but I won't be overjoyed where I lose a lot of energy. Now I'll just focus on the fight."

Here's what some names from the boxing world think about tonight's fight:

Retired heavyweight Mike Tyson: "It's close. I think Crawford will win, if he wins easy I will be totally surprised."

Middleweight Liam Smith: "I'm going to edge towards Crawford but I wouldn't be surprised with any result. They are two elite fighters at the top of their game."

Two-weight world champion Natasha Jonas: "I change my mind with Spence-Crawford all the time. But right now, it's Spence."

Former featherweight world champion Kid Galahad: "I'm going with Spence - look at the face of opponents after they've fought Spence versus the other welterweight champs."

Read more predictions here.

So how did this fight between two long-time rivals finally come about?

Coral Barry, who is in Las Vegas tonight, takes a look here.

Amit Champaneri: It’s here! The best boxing fight in this era and for the ages! Two of the very best pound-for-pound going head to head in their most defining fight! Respect out of the ring, 100% warriors in it.

Right, almost time for the big one! If, like me, you are in the UK then I tip my hat to you for getting up at this time. Your reward, hopefully, should be a classic, so who are you backing to win?

Let us know via #bbcfootball or text 81111 (UK only - texts will be charged at your standard message rate)

Coral Barry
BBC Sport combat sports editor in Las Vegas

We have plenty of stars at ringside. Just spotted British heavyweight Joe Joyce. Manny Pacquiao popped up on the big screen not long ago and there was almost a stampede when Mike Tyson arrived.

The former heavyweight champion isn't exactly ringside, he's just outside the inner circle and isn't even in the centre. Which is a bit odd, considering his stature but perhaps he doesn't want to spend all night taking selfies with people.

Which is fair.

Barry Jones is sat beside me and he's pointed out a few basketball stars to me as well. Not that any of them rang any bells for me.

Isaac Cruz has beaten Giovanni Cabrera by split decision in the penultimate fight of the night in Las Vegas.

Two judges called the lightweight fight 114-113 each way, with the third giving it 115-112.

Errol Spence Jr believes he has the "mental edge" over Terence Crawford.

The 31-year-old aims to win his first undisputed championship by capturing Crawford's WBO title.

The fighters and their teams clashed repeatedly at the news conference , with Spence branding Crawford "too emotional" as he argued with hecklers.

"I definitely have the mental edge," Spence told BBC Sport. "His team [were] heckling me and I just smiled. It comes with the territory. I'm not getting paid to fight them, I'm getting paid to fight him.

"So my attention is to him, not his coach not towards anybody else."

Coral Barry
BBC Sport combat sports editor in Las Vegas

Here is your obligatory atmosphere post...

I've been to enough shows in the US to know the majority of fans generally don't take their seats until five minutes before the main event.

As a result the vibes have been generally subdued in here. Imagine it will pick up massively once ringwalks begin. A couple of thousand fans packed out the weigh-in on Friday and made a huge amount of noise, so boxing math dictates the atmosphere tonight will be similarly feverish.

Image source, .

Terence Crawford says he will prove he is the "best fighter in the world" tonight.

WBO welterweight champion Crawford is aiming to become the first male fighter to win undisputed titles in two divisions.

"This is the Terence 'Bud' Crawford era. This is my era," he said.

"Everything about Terence Crawford is better than Errol Spence Jr. When you look at everything I do in the ring, it is better than Errol Spence Jr.

"Come fight night, I will be proving each and every one of the doubters wrong, once again, that Terence Crawford is the best fighter in the world. Not taking anything away from Errol Spence Jr but Terence Crawford is the better fighter."

Coral Barry
BBC Sport combat sports editor in Las Vegas

Both fighters just appeared on the big screen for the first time and Terence Crawford by far got the bigger cheer.

Surprising. Most people would consider Errol Spence Jr would have a bigger following, but 'Bud' is clearly well represented here tonight.

Crawford could also deliver an all-time cool entrance if he has managed to convince American rapper Eminem to come along.

The two exchanged messages on social media this week, with Crawford inviting Eminem to be part of his ringwalk.

Could it happen?

We're into the closing stages of Isaac Cruz's lightweight bout with Giovanni Cabrera, who has taken some heavy hitting but has really stepped things up in recent rounds.

There's cheers as Errol Spence Jr is shown on the screens at the T-Mobile Arena.

Terence Crawford also gets a really good show of support as he pops up the screens going through his final preparations.

A real sense of anticipation as the big fight approaches.

Watch as Terence Crawford and Errol Spence Jr exchange fighting talk during their press conference in Las Vegas ahead of their undisputed welterweight fight tonight.

Hello!

The action on the undercard is almost over in Las Vegas, meaning we are joining the action shortly before the main event.

The contest, which has been years in the making, finally features two of the world's best in the ring as WBO champion Terence Crawford takes on undefeated fellow American Errol Spence Jr for his WBC, IBF and WBA (Super) titles.

Image source, Showtime

It may be the middle of the night in the UK, but no time is a bad time for one of the most hotly anticipated fights in recent years.

Following numerous delays and postponements, Terence Crawford and Errol Spence Jr finally face off in an undisputed welterweight title clash in Las Vegas.

It has been talked about as one of the biggest fights of this generation, and hopefully it will live up to such billing.