The Great Britain racer was the starter for the run and also paced some of the runners around the seafront 5k course.
Steadman, who is based in Portsmouth, is a double world champion, and now a five-time European champion after winning the title in Austria recently.
She was a silver medallist at the 2016 Rio Paralympics and is a supporter of parkrun.
In total 366 people completed Southsea’s popular promenade 5k event on Saturday.
City of Portsmouth’s Toby Brimecome finished first in 17min 32sec.
Talented triathlete Neil Collins was second in 17.40.
Adam Chant, of Baffins Fitclub, got another good personal best with his time of 18.46.
Lots of good times were achieved and parkrun regulars Mark Ferguson (19.43) and Michelle Cartwright (20.29) both set new bests.
Another regular runner Brett Rumfitt had a great time at the 200th Southsea event and got to meet Lauren.
He said: ‘Amazing it is now 200. I ran the second one and have done 155 of my 166 here and volunteered about 15 times too.
‘Great event run for free by fantastic volunteers.
‘It has certainly brightened up my life, given my running a major boost and enabled me to meet some lovely people.’
Emma Jolley finished first lady (19.02), while Nikki Tout and Fran Marshman also got PBs for Southsea.
The event takes place every Saturday at 9am and is free to enter. It starts at Speakers’ Corner. For more details see parkrun.org.uk/southsea/