Tottenham thought they had got off to the best possible start only to have a Harry Kane goal disallowed for offside.
That was then followed by Saints having one chalked off too after an Ings handball.
But the former Liverpool man made amends on the 30 minute mark when he controlled well and fired a low shot past Hugo Lloris for the opener.
The score was level going into the break though, as Heung-min Son broke at pace and fired in an equaliser.
The South Korea international then doubled his tally for the day with a neat finish immediately after half time.
And he completed his hat-trick midway through the half, once again finishing well after being played in on goal.
Son wasn’t finish there though, and got his fourth of the day with 15 minutes remaining.
Kane had been the provider all afternoon but got one himself late on, poking in from close range.
Southampton did pull one back late on as Ings scored from the penalty spot but it was too little too late.