The South Zone of the Ranji Trophy, 1990-91, the leading domestic cricket tournament in India comprised 6 teams, all coming from the Southern region of India. All the teams had been playing in the tournament on a regular basis for the several years and they included the teams of Tamil Nadu, Kerala, Andhra, Karnataka, Hyderabad and Goa. The teams competed with each other very hard for claiming the top spot in the zone and also for securing a berth in the knock out level of the tournament. However, the teams like Hyderabad and Karnataka eventually became successful as they earned total of 85 and 77 points, respectively, at the end of the zonal level league matches.

The first of the South Zone league matches in the Ranji Trophy, 1990-91 was played between the teams of Andhra and Kerala and the match was held at Vishakhapatnam from 09-12 November, 1990. The Kerala team played wonderfully in the match and earned 11 points and won by a huge margin of 9 wickets and the Andhra team also earned 4 points from the match. The teams of Goa and Karnataka played against each other in the second match of the South zone and the match was held at Panaji from 10-13 November, 1990. The match remained a draw and the match officials awarded the Karnataka and Goa teams 14 and 11 points, respectively for the match. The third match of the zone saw the teams of Hyderabad and Kerala playing against each other at Secunderabad from 16-19 November, 1990. The winner of the match was the Hyderabad team by a fine margin of an innings and 237 runs and the team earned 24 points from the match. The Kerala team also earned 1 point from the match.

The Goa team played against the Andhra team in the next South Zone league matches in the Ranji Trophy, 1990-91 and the match was held at Margao from 17-20 November, 1990. The match was declared as a draw by the match officials and both the Goa and Andhra teams earned 2 points each for the match. The next match of the zone involved the teams like Goa and Tamil Nadu and the two teams played the match at Margao from 23-26 November, 1990. The drawn match saw the Tamil Nadu team earning 7 points and Goa earning 5 points from it. The Karnataka and Andhra teams then played against each other in the next match of the zone and the match took place at Davanagere from 24-27 November, 1990. The Karnataka team earned 23 points from the match by winning it with a huge margin of an innings and 33 runs and the Andhra team also earned 5 points from the match.

The match between the teams of Hyderabad and Tamil Nadu was the seventh of the South Zone league matches in the Ranji Trophy, 1990-91 and the match was held at Secunderabad from 24-27 November, 1990. The Tamil Nadu and Hyderabad teams earned 10 and 6 points, respectively from the match, as it remained drawn during the specified period of time. The next match of the zone involved the teams like Andhra and Hyderabad and the match took place at Cuddapah from 01-04 December, 1990. The match was won by the Hyderabad team by a narrow margin of 3 wickets and the team also earned 22 points from the match. The earnings of the Andhra team from the match were 9 points. Then the teams of Tamil Nadu and Karnataka played against each other in the next match of the South Zone and the two teams played the match at Coimbatore from 02-05 December, 1990. The drawn match saw the Karnataka and Tamil Nadu teams earning 6 and 3 points, respectively from it.

The tenth match of the South Zone in the Ranji Trophy, 1990-91 was played between the teams of Kerala and Tamil Nadu and the match took place at Palghat from 08-11 December, 1990. The Tamil Nadu team earned 25 points from the match, by clinching a victory of 99 runs and the Kerala team also earned 3 points from the match. The next match of the zone saw the Hyderabad and Goa teams playing against each other at Secunderabad from 11-14 December, 1990. The winner of the match was the Hyderabad team with a margin of an innings and 211 runs to earn 24 points and the Goa team earned 3 points from the match, as well. The Goa team appeared in the next match of the zone also and this time, it played against the Kerala team at Thiruvananthapuram from 20-23 December, 1990. The Kerala team won the match by a margin of 35 runs for earning 16 points and the Goa team earned 6 points from the match, as well.

The Karnataka team then played against the Hyderabad team in the next match of the South Zone and the two teams played the match at Dharwar from 23-25 December, 1990. The Karnataka team earned 13 points from the match by clinching a victory of 76 runs and the match also saw the Hyderabad team earning 8 points from it. The next match of the zone saw the Tamil Nadu and Andhra teams playing against each other at Madras from 02-05 January, 1991. The winner of the match was the Tamil Nadu team with a huge margin of 10 wickets and the team also earned 18 points from it. The Andhra team earned 4 points from the match, as well. The last of the South Zone league matches in the Ranji Trophy, 1990-91 involved the teams from Kerala and Karnataka. The match was held at Thalassery from 05-08 January, 1991 and The Karnataka team won it with a huge margin of 252 runs. The Karnataka and Kerala teams earned 21 and 7 points, respectively from the match.