The Swans moved back to the top of League One with an awesome performance at Roots Hall that saw Lee Trundle out-gun Southend hot-shot Freddy Eastwood.
All eyes were focused on the two hottest properties in League One before this top-of-the-table clash kicked off, but it was Trundle who came out with his reputation not only intact, but further enhanced.
Trundle grabbed his 15th League goal of the season and set up strike-partner Adebayo Akinfenwa with a bit of magic for Swansea's second.
"Trundle was tremendous," said Southend manager Steve Tilson as his side slipped from first to third in the table. "He was the difference between the two sides and put in a great performance for Swansea. We gave the ball away and then allowed him too much space.
"Swansea's second killed us off and we never got to grips with them.
"In the last ten minutes maybe we could have nicked a point but with hindsight, on the day, they deserved the win."
Swansea dominated the opening stages after Swans boss Kenny Jackett recalled Garry Monk to the heart of the defence at the expense of Kevin Austin, while Kristian O'Leary was preferred to skipper Roberto Martinez in the middle of midfield.
The crucial breakthrough came five minutes before the break when Trundle latched on to a header from Owain Tudur Jones to fire home.
Things got even better for the 1500 travelling Jacks when Swansea extended their lead two minutes after the break.
Trundle worked his magic on the by-line to somehow squeeze his way past three Southend defenders to drill the ball across the face of goal for Akinfenwa to apply the finishing touch from close range.
Southend slowly started to come more into the game after the hour-mark and Eastwood missed a great chance with a free header.
They did manage to pull one back nine minutes from time when Willy Gueret failed to hold on to a Wayne Gray header and Eastwood volleyed home from close range.
But Swansea never deserved to lose this one after such an impressive performance in front of a sell-out crowd, a point not lost on Kenny Jackett.
"Goalscorers tend to get the headlines and Lee played very well,'' he said. "But there were some other big performances from my players as well.
"It was a really big day for the club and it turned out fantastic. Everyone should be proud of what we have achieved - and enjoy it.
"Now we must make sure we capitalise and build on what we have achieved so far - starting against Yeovil on Friday.''

Southend: Griemink, Hunt, Edwards, Barrett, Wilson, Campbell-Ryce, Guttridge (Bentley 68), Maher, Cole (Lawson 79), Eastwood, Goater (Gray 68). Subs not used: Prior, Smith.
Booked: Barrett, Campbell-Ryce, Wilson, Bentley.

Swansea City: Gueret, Tate, Monk, Iriekpen, Ricketts, Britton, Tudur Jones, O'Leary, McLeod (Robinson 88), Akinfenwa, Trundle. Subs not used: Austin, Forbes, Martinez, Connor.
Booked: Tate, Monk, Iriekpen.

Ref: D Deadman (Cambridgeshire).

Att: 11,049